I bought one a few years ago. It was about 10" x 5" and had 2 maybe 3" fans mounted on the aluminum panel. Had an alligator clip to hold it on to the evaporator fins. Bought it on ebay.
This is a link to a picture:
https://www.bing.com/images/search?view=detailV2&ccid=K6cLNPeG&id=BF7CF1804272FDC4EDD0DB24CA8A1CBBD267BE4C&thid=OIP.K6cLNPeGRO6EEIl0nXu5rwHaFj&mediaurl=http%3a%2f%2fi.ebayimg.com%2fimages%2fi%2f252065200750-0-1%2fs-l1000.jpg&exph=750&expw=1000&q=camper+refrigerator+fan&simid=608004734037264026&selectedIndex=2
It wasn't too good. Nothing there to protect the fan blades. We put a lot of food in the frig. Fan blade broke off in a week or two.
I think I only wasted about $12. The old D cell camco lasts about a month on a set of batteries and has been working for us for about 10 years.
Joe and Evelyn