WAY too small. The smallest I would ever concider buying would be a 5.8-6.0 cu.ft. These can easily fit two cornys with only minor modifications if any.
I think I've seen 4.3cu.ft. dorm fridges used around here, but they require you to remove the freezer and mess with the coolant lines, which I don't suggest unless you know what you're doing. You could easily ruin your fridge.