Yep, we have an Evakool; 7-L camping fridge/freezer that draws 5A@12V and will definitely freeze soft drink bottles of water.
A lot have compressors these days, if electric only. Somehwere on myswag.org is a project by a bloke who built his own freezer (?)/fridge with compressor and glycol(?)
Parents have had a string of those little things and after the first warm stuff event, mum started treated them just like an esky with pre-frozen blocks of stuff in them. Eventually she got dad to realise they were a waste of money and they have returned to a simple esky now.