We have had pretty good luck by just making sure the air circulates throughout the fridge. I have seen several inexpensive fans like the one pictured below. That is the one we are currently using since we accidently let our other fan go away during the trade in process. Not sure if it will keep your items from freezing but we haven't had anything freeze yet and everything stays evenly cold throughout.
Valterra A10-2606 FridgeCool 11.28 mA Fan with On/Off Switch