Sounds like the RV repairman has not kept up with the world of offroading or options available for slide-in campers.
I have used compressor fridges for years as I am normally over 2 hours from any ice machines. Here is an aussi article that can explain answer most questions.
These are portable and the next link is for built in units from truckfridge.
https://www.exploroz.com/Vehicle/Accessories/Fridges.aspx?s=fridge
http://www.truckfridge.com/tf130/
