Get a compressor fridge. Difference between the ebay ones at ~500 and the brand names ones at ~900+ are the compressor and insulation.
I have a mate with an ebay cheapies - consume twice as much power but has not broken (now a couple of years old). Brand name fridges use mainly Danfoss compressor or Engel which has their own compressor, both seem to be pretty reliable.
Waeco (Domestic) are now sold under several 4x4 brand names with subtle differences such as hinge mechanisms and all use the Danfoss compressor. ARB, Ironnan etc.
I got the ARB, clever detachable and robust hinge on the lid and it's orientation makes a world of difference to it's usability. Think about how you will mount (slide?) and maintain airflow (cooling) before you buy it, there isn't much room in a JK...