Flash Flag

(sorry about the load time, the instructions are big files)

Flash Flag

Close-Up of Clamp

Installation

Clamps onto seat stay. The company also makes a rubber insert to use the clamp on rear rack tubing, which they will send you free with a SASE (not sure how you put Canadian postage on it though)! I'm going to order some of them. You could also just use a strip of rubber from an old fashioned tire patch kit. You can also cut the round part of the clamp off and mount it to a flat surface with the screw.

Scan of Instructions