I really like this strap-based handlebar mount for my GoPro cameras! The rubber, strap-based sizing system is superior to most others I've tried.
I've got a few different bicycles and motorcycles I like to mount GoPro cameras on, and different diameter handlebars make that a pain. Other mounts I've tried use various adaptors and sizing rings to try and get a snug, vibration light fit. This strap mounted system works great! The strap is easy to use and fits in places where maybe there really isn't enough space.
Arkon GoPro Bike Motorcycle Handlebar Strap Mount for GoPro HERO Action Cameras via Amazon