It turned out the previous version of the USB camera mount lacked sufficient griptivity to hold the ball’s position against even moderate bumps, so the upper “half” is now tall enough to hold a lock screw directly over the ball:
It doesn’t look much different:
A view from the other side:
The previous iterations used Genuine 3M foam tape, which seemed too flexy for comfort. This one sits on a bed of hot melt glue and is absolutely rigid. We’ll see how long it survives.
Tightening the cap screw requires needle-nose pliers, because the whole affair has no room for a hex key.
The OpenSCAD source code as a GitHub Gist: