So I was looking for a bigger fridge for my trip and got 60 liter "CIGREN" for only $610
https://www.amazon.com/gp/product/B07MS8TLVT that is a true fridge/freezer.
It's kind of big, but sort of fits into the recessed area in the trunk. There's some space under it there for some loose items that you don't need during the trip itself and it obviously is higher than the area. If you remove the "fake 5-seater floor" and drop in a large suitcase (28" I think, it's the biggest one I have) between it and the fridge - it forms sort of a flat area even.
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The flat area is also convenient for other things, like a make-shift baby changing tray or some such.
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So far I only have it for 2 weeks and one roadtrip so who knows how's the longevity, but otherwise I am really happy with it.