Its pretty silly to not buy a motorhome because it has a Norcold fridge or Dometic for that matter. Install some type of fire suppression for a few hundred bucks and sleep well. Worst case, if you are that afraid of it, once you buy the unit, go out and have a heavy duty absorption cooling unit swapped in. The heavy duty units use much thicker steel, and are much less prone to bursting.
If you are that afraid of it, you probably should not buy a motorhome with a transmission. Transmission fires are the number one cause of RV fires. Maybe get rid of the engine while you are at it.