I'm still confused. Does anybody ever just check to see how well a simple inner-tube scrap will work as a rubber/o-ring?

Simply put a piece of rubber around the flashlight body, and then use O-rings made out inner tubes.

Its superior to these other mounts, its adjustable on the fly, and it costs next to nothing. (use a second band as necessary for security or firmer setting.

Aw, never mind, better to buy than build.