I broke the screw-in mount for my left mirror. After much searching I found a clamp that looks like it will do the trick from these guys: http://www.kevinscycleracing.com/.
Go to the Lights/Signals page and look about 3/4 of the way down the page. Only $7, plus $5 shipping. Not bad compared to the cost of OEM ! What are they thinking with the costs on OEM stuff?

Anyway, thought I'd share. Kevin's looks like a good online shop. Nice to talk to on the phone too.

 

I got one thru a member for the cost of the shipping. A lot of us have removed a lot of stuff off the bikes which is just siiting in our garages so next time something like that happens just post up a request and you might get lucky.

 

I got mine from a can am dealer I paied 9.99 for it