compressor fridges are what you want - they work well and will work at angles
common caravan 3 way fridges take alot of amps on 12 volts and so need gas when parked up and have to be level. they also run on 2f40v but you'll need a genny or hookup and they are not the quality to sand up to rugged use
so what you need is a low wattage , probabily chest type fridge from the likes of engel, minus 40, national luna, shoreline, waeco (order does not imply any recomendation or preference) and of course how much space you have, my 101 landie had a 40litre minus 40 which was brill , others swear by engel etc etc
so if this is the size then it probabily pulls 12-20 watts an hour you'll be fine
Iveco Turbo Daily 4x4 40-10
Ex Owner LR101 300Tdi Ambi 'Tiggurr'