8BitDo's Micro Bluetooth gamepad [8bitdo.com] is the follow-up to the Zero, a similarly tiny wireless controller that I reviewed years ago—I liked it, but it had some problems. From reviews, the Micro appears to have solved all of them but for the unsolvable one—hand cramps!
It's compatible with Switch, Android, RPi/Linux, Windows and MacOS, supports button mapping through included software (on Windows), offers 10 hours of play on a 1-2 hour charge, and weighs just under 25 grams. Comes in blue or green for less than $25. Note that it doesn't have vibration, motion sensing, console wake, or anything else you really can't expect to stuff in such a teeny box.
Though I don't have one, yet, I know the range on these isn't great. Maybe 6 ft. They're for on-the-go gaming, not whatever remote control shenanigans you might be dreaming up.
8BitDo Micro Bluetooth Gamepad [Amazon link]
