Rather than try to cut into the wiring, I bought two Valterra fridge fans, which run from a pair of "D" cell batteries for about 4-5 weeks, stuck one in the fridge part, another in the freezer. They don't move much air, but in such a small space, they circulate it enough to move the cold air at the bottom of the fridge around to keep things cool.
For fridges that are relatively narrow, like some tall ones in the Winnebago ERA and Travato 59G, I recommend two fans in the fridge compartment, one set lower, otherwise the cool air will just pool at the bottom.