I installed a Garmin Zumo 550 GPS on my Yamaha TW200. I used the rugged Touratech locking GPS mount. The Garmin credial is hardwired into a switched 12v circuit. This allows the Zumo to turn on automatically when the ignition key is turned to the on position.
TOURATECH's Zumo motorcycle mounts offer increased security to protect the plastic Garmin cradle. It is designed to bolt to a 1/2" crossbar, but can be adapted to almost any motorcycle with a RAM system. Key Lock provides more security while filling gas, etc.