The Xiaomi sub-brand Black Shark has a new accessory: the FunCooler Pro. This, as it may sound, is a smartphone attachment with a fan intended to manage device temperatures while gaming. It has adjustable clamps, and may thus fit onto the backs of phones besides those of its own series.
https://www.notebookcheck.net/Xiaomi-s-Black-Shark-releases-the-FunCooler-Pro-for-gaming-phones.459142.0.html