Using Upfitter switches to power my extra frig on the road?

I'd go the inverter route as well. Dorm fridges don't draw that much power. I just put my Kill-A-Watt on my 'counter height' fridge we have in the basement rec room and it pulls about 55 watts/.7 amps. You don't need a big solar bank for that but just be careful how long you are running it as you drive so you don't drain the battery. Also not sure how much the truck will supply to charge the battery so might want to be careful the first time. A 500w inverter with the proper size wiring should do the trick.