I did a nice ride 2-up with my wife 2 weeks ago to Vermont, New Hampshire, Maine, and I didn't have a GPS.
I had the power plug installed on my custom plate:
but I didn't have the GPS still.... I only had my Garmin nuvi 650 that I use in the car. No way to spent 700$ on a "motorcycle" GPS....
It was too late to buy a support from speedy or anywhere else...
Conclusion: I had to find something that will work... how about some tie-wraps?
what about rain?? How about a ziplock bag??
The trip was great, the GPS worked like a charm, we had some rain-storm that got us pretty soaked... but GPS stayed dry and worked all the way.
When it didn't rain I had the GPS without "rain protection" because the sun was making the screen very hard to read, when raining I had the zip-lock on, was easy to see the screen.
here is the GPS installed on Versys for less than 1$ ( I don't count the power plug