Hi
We fitted a single 8 cm computer fan to the outlet for our 12v compressor fridge which kept cutting out due to the heat. This was in France and Spain with temps at 30C most of the time. Worked perfectly.
We then fitted an additional absorbtion type fridge, 12v, 240v and gas, and again fitted a fan. The fridge got a lot colder due to the heated being extracted away and we managed ice cubes from it whilst parked in temps of 30C
Just an ordinary cooling fan for a PC..even buy them off e-bay for a couple of quid.
Cheers