My last motor home I band clipped a fan on the bottom of the bottom shelf blowing up. It was behind a cutout for gallon jugs and I didn't think anything would ever end up in that small space.
This one has no cutout but does have a very narrow shelf below the cooling fins, the fan is mounted on the bottom of that shelf blowing up.
The link below is the fan I used this time. Ball bearings will last longer than sleeve bearings, important when something runs 24 hours a day. The refrigerators aren't very large, a fan that moves 15-20 CFM will generally be 2-3 times the refrigerator volume and keep the air stirred up sufficiently.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
If you pull the cover off the light you can find power before the door switch and a ground, the fan above only uses .3 amp so it will easily run off the light wires. No batteries to change, it runs as long as the refrigerator is turned on.