This is what i do,
I have an inside the fridge fan. I turn it on, LOL! then i stock thenear top shelf with 4 or 5 ice packs. remember that cold air sinks. and seeing that your fridge has no circulation this is key. i leave a gap so the little fan can move the air near the fins in the reefer section. I put a 1 gallon frozen jog of water in the freezer. Come back in 4-5hrs... and reefer is to temp.. while camping i also have two or three 18oz water bottles that i rotate from fridge to freezer.. it helps stabilize the temp as well.
HTH