If you're looking for budget options with positive reviews, there's Whynter.
https://amzn.to/2AL2xHo
If, like me, you're down to try a no-name generic, check out Costway.
https://www.costway.com/54-quarts-portable-electric-car-cooler-refrigerator.html It's most affordable straight from the web site, but if you buy it through Amazon, you can purchase a third-party warranty, which may give you more confidence in buying off-brand.
https://amzn.to/2VUSR69 I snagged mine a couple months ago.
With 50º ambient temps, the fridge maintained 34º for 55 hours on my FJ's Optima Yellow Top. This was on less than ideal wiring, so performance may have been hindered. I've since added an additional 12v port in the interior and given the refrigerator a dedicated (fused) homerun to the battery. Given the cold ambient tempts, it's hard to say just how well it really cools or how efficient it might be, but my drinks have stayed cold and my food has stayed fresh.
The way to really justify a refrigerator purchase is to put it in the vehicle permanently and use it all the time. Aside from drinks and snacks at the ready, it has been convenient for transporting medication and for being able to make stops between the grocery store and home after purchasing items that need to be kept cold. I'm glad they're appearing at reasonable prices now.
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