I'm in the process of construction a holder so that I can use my car sat nav on my bike.
I'm going to use a 8 x 100 bolt, cover in duct tape to make a very tight fit for the hole in the head stock on my bike.
This will go through a pre cut piece of thick plastic which will be covered in Velcro, pop some Velcro on the back of the sat nav and vola.
Maybe.
Also for charging, instead of fitting a 12v socket to the bike I'm thinking about trying a small solar panel to help charge the Sat nav.

Should be finished by this weekend.