I suggested freezer and not refrigerator because there is more clear workable space in one.. a refrigerator would work also..
Just do not forget the danger aspect of kids getting trapped inside.. (ref: comment about laying one on its back)
You can buy replacment heating coils from chicken catalogs.. a light bulb is not very energy efficient as a heat source.. by the time you wire 2 or three lights in there, you can purchase a heat coil.
Or do like I did..tear the guts out of a styrofoam bator and use them.
also, wire the fan to blow continuously.. wire only the heat coil through the thermostat..
I rewired some of my foam bators that way.. I think the heat stays more constant that way..
........jiminwisc.......