GoPro tripod mount
Fits the Hero 3+ as shown and standard 1/4-20 thread like a tripod mounting plate. I don't own any other GoPro. It may fit other models just fine.
But it's not a simple 3D print. The black is SemiFlex by NinjaFlex. It's tough material. Holes are not easy to print. A couple of holes need to be punched out after printing. The brass insert is best heated before inserting. It provides half an inch of thread depth.