Maybe hooking it up to the headlight socket with a kill switch might be better so when your not using it it can be shut off rather than having it on at night and you have no use for it and save your battery!I just received my Garmin 220 GPS from Amazon. I don't have the bike yet so I'm guessing.
It looks like the easiest way to mount the GPS is using the included mount on the left clip (handlebar) near the clutch cable bracket. It looks like there is space there for the u-bolt used on the mount. I may have to come up with something else when I get the bike in a few weeks. I'd planned on getting power from the headlight socket on the back of the headlight. It's on when the bike is on and goes off with the key. It's probably easy to get to as you need easy access to change the headlight bulb. I'll just have to see when i get the bike.
Let me know what you decide as I need ideas, also.