I use an Eye of Mine clamp, but for some reason they discontinued them. http://www.eyeofmineactioncameras.com/product_p/rrlb-rp.htm
I would look at the getting one of the new GoPro roll bar mounts. They seem quick and easy to change out to different locations. The head rotates too.
https://shop.gopro.com/mounts/large-tube-mount-roll-bars-plus-pipes-plus-more/AGTLM-001.html