I just made a plywood base, attached the VC to that with a G cramp arrangement then strapped the whole lot to a tank bag. Gave acceptable results (even better before reducing quality for youtube):
http://www.youtube.com/watch?v=73U-kdd4pfYalthough as it slipped to one side some of the cornering looks somewhat lurid!
I've since bought a cheap device from Morgan Computers:
http://www.morgancomputers.co.uk/Shop/detail.asp?ProductID=6018which I have yet to find a way of fixing to my helmet.