Bonneville America Forums Forums Technical Forums Accessories red light changer - where to put it?

I picked up one of these things Amanet Red Light Changer recently. Seems like a good idea and not too expensive. However, I can't seem to find a good place to put it. Instructions say to attach it to a 1" diameter flat piece of metal. Can't seem to find one of those on the bottom of the bike other than the oil filter.

Any ideas?