Yep, finally scratched an itch and put together a portable power supply. Of course I know that they are already built for the purpose as "jump-starters", the better examples of which have built-in inverters and 12-volt outlets on them.
For providing quiet, light-duty power for a variety of purposes, you don't want a "jump-starter", and the reason is obvious: they have flash-type batteries, the type designed to start cars by providing a lot of amps quickly. That design has serious deficiencies for providing power over the long-term, in lesser amounts. for that purpose, you need a Deep Cycle battery as your primary power. Such deep-cycle batteries can give twice the power that an equivalent weight-and-cube Starting Battery can, they just can't crank out the amperes in the hundreds.
So, in creating the "perfect" power supply (yes, I do in fact, have an ego!), I looked for something that wouldn't pull my arm out of it's socket carrying it. Goal accomplished, the RPS-01 weighs 28#, together with it's charger, a light inverter, a "heavy current" transfer system (up to 30 amps), a double 12-volt female adapter. Not in sight in the second photo is a 12-volt extension cord. I have one on my boat and will place it with this kit.
This photo shows the Plano Ammo Box the kit is enclosed in. Note the 12-volt outlet which I installed on the top.


The second photo above shows the box, ready to go. The battery is enclosed and wedged in with closed-cell styrofoam, one piece beside the battery vertically, and another on the bottom of the box under the stowed auxiliary equipment. You can see the 750-milliamp charger in the equipment well.
This photo shows all the equipment that packs into the kit. From left to right: The Battery Tender 750 MA charger, with it's "flat-two" connector system, a 10-foot 110-volt extension cord with triple-tap, a double 12-volt female outlet adapter, a "flat-two" heavy 30-amp adapter, currently fused for only 15 amps until I get proper ring terminals instead of the clips on the adapter now, and a Chicago Electric (from Harbor Freight) cheapo 80-watt inverter with USB-power outlet.

I will carry other inverters, namely these three in the photo below. You want to suit the inverter to it's load, because the inverter's idle current consumption goes up as the size (output) of the inverter goes up, and that idle current makes it a power hog to use, say, the 400-watt inverter to recharge a cell phone.

From left to right, those are a dependable (old) West Marine Sorcerer 250-watt (no fan, very quiet), surges to almost 400, will carry a 4.0 cu/ft Haier fridge (had that combo on my previous boat); a 400-watt Chicago electric model, surges to 700-watt, with USB, haven't used it other than to test it (fairly quiet fan, though); and a Statpower (Trace) 175-watt inverter, very reliable, but it's cooling fan screams it's not-so-quiet song, can be heard for 50 feet, but it's reliable, has hundred of hours of use powering an former, power-hungry laptop that used 90 watts. All these inverters are out of my stock of preparation materiel. The Chicago Electirc 400 is current ($59 at Harbor Freight), the other two, not current.
So, I have inverters from 80 to 400. I have others, a 750, a 800 and a 1,500 watt, but they won't work well with this size of battery. They work with 2 X Group 27 battery lash-ups, of which I have several sets, but they are a whole different deal, very heavy, you don't move these without a Second Soldier to help you.
The battery itself is the Absorbed Gas Mat (AGM) type, and this model, the Batteries-Plus Werker Model WKDC12-35J, rated at 35 amp-hours. I chose this battery because it fits into the Plano box easily, and is quite common, being the most widely-used mobility-scooter battery.
Work left to do: I want to get one of those digital voltmeters that go into the 12-volt receptacle and carry that and I need to fuse the heavy-current output for 30 amps after I provide proper conduction for that current (ring terminals).
Cost to construct:
Case: the Plano case sold new for $15.00 on sale, $20 not on sale. It is sealed with an o-ring, and is designed to carry this level of weight in shotgun shells. It is the size of a USGI 50-cal ammo box, but it's made of polystyrene, and non-conductive, not affected by any acid fumes.
Battery: It was $80 at Batteries Plus.
80-watt inverter: $20 at Harbor Freight.
Charger: This advanced, 3-stage float charger with polarity reversal protection cost $40 at Batteries Plus. First quality equipment.
The extension cord and double-outlet for 12-volt added up to $15. The "flat-two" adapter was part of the battery charger, no additional charge. Heavy-current fusing (not yet installed), another $20 for holder and two spare fuses.
Total expended for the kit: $150. Labor, maybe 3 hours so far.
Yet to add, a proper fitted "boot" for the positive terminal of the Werker battery. These are hard to find, and I may have to find a specialty jobber. Small money nvolved, maybe $5. The plug-in digital voltmeter, if they are still available, will be no more than $20. A small "ditty bag" to carry the extra inverters and whatever else I want with the kit (have many of those in stock already).
Power stats:
This battery is nominally rated at 35 amp-hours at a 20-hour discharge. So, 35 X 12 X 20/12 = 700 watts deliverable @ 12 VDC to zero capacity. You never want to discharge this type of battery below 50-60%, so that's 350-400 usable watts at 12 volts down to recharge voltage. The only downside to this battery is that it's recommended recharge rate is 1/10th capacity, or 3.5 amps. You can hurry this up a bit if you monitor the battery's temperature (using a non-contact, infra-red thermometer, about $40 at harbor Freight), but since it's a sealed battery, you don't want to have it out-gas during recharging, so it has a max charging temp of 77 degrees ambient. If it's cold, you can bump up the charge rate some, but if it's hot, you have to cut it back. This battery would charge beautifully with a 45-watt solar charger, costs $150 at Harbor Freight.
There you have it: a quiet means of providing power for your electronics so that the zombies don't hear your generator running and flock to the blood it represents, forcing you into a Zombie Apocalypse shootout....