I bought mine off ebay. Right off the top of my head I don't remember who made it. (possibly Kuryakyn or Custom Chrome) It clamps to the frame and is actually designed for a cats eye tail light. I just made an extension from some stainless steel that I had laying around to mount my maltese cross tail light to it. I'll see if I can find the manufacturer.

http://s902.photobucket.com/user/splitt4neb/media/kickin%20it/DSC_0459.jpg.html?sort=3&o=9

In a civilized country, wild animals only continue to exist at all when preserved by sportsmen. The excellent people who protest against all hunting are ignorant of the fact that in reality the genuine sportsman is by all odds the most important factor in keeping wild creatures from total extermination.

Theodore Roosevelt