"use a FridgeMate fan built for the purpose.  They have both 12v and battery
models -- the battery one will run for 30 days on two D cells."

I have one of those (D) in my vitrifrigo. I can put so much stuff in it that I think the circulation helps .... but there's still not enough room for a dog ....but steaks stay frozen in the freezer .... so there IS enough room for a steer.

bob