I made this super simple GPS mount for my bike out of some scrap metal that was painted with metal-texture spray paint. With clip-ons its hard/impossible to fasten the handlebar mounts, so I made this little metal bracket that has a hole in it for my screw on gas cap. Under the mount is some adhesive foam rubber to protect the paint, and on top of the mount is a rubber gasket to keep the fuel from spilling around the cap. I added velcro the to top of the mount and to the back of the GPS unit. Works great!

Of course for those with quick fuel type caps that flip open, this wouldn't work. But you could make a version that has holes for the allen head bolts to fit through.



wide shot:

 

looks good...but ive noticed the gps units only last for like an hour or so off the charger...make a charge to run to your battery and that shit would be golden!