The most overbuilt option is probably this: https://www.noctua.at/en/products/nv-fs1

You can mix and match components because at it's heart it's just a PC fan in a custom frame.

5 volt computer fans are a very common thing. You can get good ones with ball bearings (more expensive) that are intended to run in servers for years nonstop.

How big are we talking? I've got a USB desk fan from a subscription box a friend had, that's basically just a computer case fan in a 3D printed housing, and it's lasted me years.

Arctic makes decent ones (just google "Arctic usb fan"). At least the electric/motor was no issue (i abused the casing much). But not sure if it's Europe only and if that's a problem for you.

Not a recommendation, but you should look for a big fan, not a small one. The bigger ones are a lot quieter, as they don't need to spin up as fast to push the same amount of air. The tiny fans sound like jet engines, please don't get one of those!

Alternatively, you could go with a fan that you flap with your hands, they usually fold up neatly and you don't need to go looking for a USB outlet. Perhaps not as convenient though

12V 120mm ventirad fan directly soldered to raw USB-C connector. USC-C cap current to 100mA if the cable doesn't have USB controller, so no risk of electrical damage (in theory).

The fan has maybe 10-20 years old. It comes from my fan box (you know, the one next to the cable box). It's so silent I regularly forgot to turn it off, and it may run for days before I notice 😅

Those could put some high voltage into the phone and damage it, just don't.

Sorry for the bad wording, need sleep, lol