We tested how various Garmin GPS units fit on Ducati DesertX with Perun moto GPS R12 mount - Garmin Montana 6xx, Zumo 396 and Zumo XT.
They all fit great, check it out.
In the user manual that came with the Ducati DesertX, there is no word on how to wire a GPS unit to the bike.
This is how I wired Garmin Zumo XT. It is fairly easy if you have basic soldering skills.