The GoPro!

This fixation perfectly meets the need, and more.
It easily attaches to any tube, so as it is not too big.
So this is perfect on the part of an ATV under the seat or handlebars. It is a bit limited on the gallows ...
Also try to fix at the wheel on the fork, impressive views along floors :-)

I'll also use it to attach the GoPro ski poles :-)

Tip: Try to put a small rubber band between the tube and the fixing for better decision and avoid having to shake like a brute :)