On long river and fishing trips, a standard cooler can work with the help of a good shady spot and a towel that has been dipped in the river and draped over it.

Evaporative coolers were popular in Australia before the widespread availability of electricity:

https://en.wikipedia.org/wiki/Coolgardie_safe

A smaller version is useful for storing insulin on the go:

https://shop.diabetes.org.uk/collections/frio-wallets

I don't think they're evaporative. Plus you need to recharge?

Also, "patented crystal technology" what?!

They are, you soak them before use to 'recharge'.

Oh I appreciate you chiming in! I had no idea these existed.