"I really want to mount my GoPro onto my bike, but I'm too tight to go and buy a cheap Chinese plastic mount..."
...was the challenge I set myself a few years ago. This was at a time in my life where I as taking an unusual sabbatical that involved training to be a cabinet maker so I was 100% into making stuff myself.
The answer was sitting in my tool kit, a large Mole Grip Vice. I set about drilling a hole in the handle, buying a small tripod head, chopping bits off, strapping together with cable ties, replacing cable ties with nuts and bolts and eventually ending up with a pretty decent GoPro mount that was versatile enough to go almost anywhere on the bike. As long as I didn't mind it taking big chunks of paint out of wherever I clamped it on.
It was heavy, too big for my small panniers and in the end probably cost more than the cheap Chinese plastic mount that I was too tight to buy, but FAR more satisfying to make.