Verne,
Picked up an old used Igloo cooler/warmer for $5. Motors kinda noisy, must have a gearbox.

Spliced in a deans connector to the power cord. Can run it off the cigarette lighter or power supply. Abot 13" long inside, 8" wide, 12" high. Tested it for about a half hour, and it was warming up pretty good. To heat or cool you just reverse the plug. Will be trying it out pretty soon, weathers been kinda crappy around here again. Will have to see if the generator/power supply can handle the cooler and 2 chargers at the same time.