I do have a transit bag on my Indel B 50. One of the other fridge companies makes a bag that fits the Indel pretty well. Got it from Adventure RV but don't remember the brand. The cover has a sort of cordura exterior with some insulation, and a reflective foil on the inside face, velcro closures and some pockets on the outside for power cords and such. Cost about $55, and it works. I see a noticeable difference in fridge temps when I don't close the cover. Our climate is always hot when we are out in the PW, and heat and humidity can be real high all at the same time. Two years ago we had about 115F and rain simultaneously, and a few years before that 118F with rain. Last year the fridge saw 110F+ with a fair amount of intense rain (Arizona monsoons coming off the Gulf of Mexico), and there was no condensation of any kind on the bag or on the fridge seal. We were eating afternoon ice cream bars in the desert.
It was over 105 today at home and the truck is parked out front with a load of tuna that a buddy caught on Thursday. Fish went in on Friday afternoon, was frozen by Friday evening, and we are eating it as fast as we can because the house freezer is full. Fish is rock hard, but I have the truck's house batteries on a small charger to keep up with the heat.