I made my own solar fridge by wrapping a large stainless steel bread bin with wet towels.
Mark one went to France with me last year & had limited success. I'm modifying it for a mark 2 this season. I would like to buy an EasiCool unit, but can't afford one right now. I've been told they worked quite well, but only if you know what you're doing with them.
3 way fridge is your best option by far, but expensive.
Once you've got it you've got it though, & it will last you years.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.