if my 12v Isotherm fridge fails I'll probably replace it with an Engel. They make one that should fit nicely in this space, which is fairly deep. I would put it on slides and have a way to lock it in place. The Isotherm uses a Danfoss compressor and is fairly efficient also, but it lacks enough insulation and I think a top-load would also reduce cool air loss when it's opened.