I designed a GoPro mount for those with Syncros saddles. It improves on the official Syncros mount (which is $20) in a couple ways. First, it places the camera in a spot where its M5 bolt can be tightened/adjusted easily. Second, my mount includes indentations for the M5 bolt head and nut. This makes tightening the bolt a lot easier as you don't need a wrench to hold the nut, and there is more margin for the bolt length. I recommend printing it with ASA filament for the UV resistance.

You will need two M4 x 16mm bolts to attach the mount to the saddle.