(I guess it's a variation on Sterno-- does that need venting too? I've often wished I could brew my own fresh hot chocolate in a hockey seat!)
We have a neat mini-fridge-- dunno if these are still made, but it was built and marketed to hold a sixpack of canned beverage. Like Coke or beer? That is literally all the room it has, but it looks like an old-fashioned white fridge with rounded top, exterior handle, etc. It's a heat pump thingie. I've taken it in case motels don't have refrigeratiuon. It holds more than I might have thought-- not a styro leftovers box but then we carry baggies, so....
Coleman makes a very nice regular-cooler-sized electric cooler, that can be used upright (lets all the cold out whenever you open it), or (as we use it) as a chest to hold the cold. Runs all day fine, no issues except it does pump out a little warm air, out the heatpump flow-fan. And they do make a smaller one, not as small as my mini-fridge but smaller and cheaper than the bigger Coleman or a heavy ole bar fridge. When the mini in my office craps out, that's what I'll get. They also come with an adaptor to run off your car's lighter, or other 12-volt outlet, and I have seen many more 12-volt thingiges at truck stops that they use in those 18-wheeler palaces the drivers sleep in nowadays-- another place for Kitchenless Cooking.