Hopefully I’m allowed to link stuff. I got the below:
KDD Switch Pro Controller Clip Mount for Nintendo Switch/Switch Lite, Adjustable Clip Clamp Holder Mount for Nintendo Switch Pro Controller
One tip I’d have for it also. Don’t take it on and off. Though it’s sturdy plastic it’s likely going to get worn out and be unable to clip. You can pivot the mount to the back of the controller so it’s out of the way.