Twofish makes a couple- you just got to make sure you get one that will work with the diameter of your flashlight. You could also go with something less elegant- hose clamps or a section of old inner tube.

This is the mount that I got for my Trustfire. I was dubious of the design of the mount at first, but it has been rock solid. The light simply won't bounce out during normal operations- a crash may cause the light to pop out, but mine didn't when I took a tumble crossing over some railroad tracks a few weeks back ...