I didn't see one of these posted, but here is one my cheap, easy solutions that I use for my GoPro.
I sourced my materials from Home Depot/Lowes.
1/2" x 36 PVC Pipe (threaded both ends).
1/2" Cap (also threaded).
1/4" 20 Bolt & Hex Nut (1/4"-20x5/8" to be exact).
3/6" Eye Bolt & Hex Nut (3/16" x 1 1/2" to be exact). This is for a optional strap mount.
2 Split Locks.
GoPro TriPod Mount.
Drill & Drill Bit (1/4" Drill Bit & 3/6" Drill Bit).
Screw Driver & Wrench.
$10-$15. Addition $ for a handle bar grip, that can be found at a local bike shop.
These monopods are very VERY sturdy. I have take full-torqued baseball swings with nothing coming loose or flying away!