I use a Garman Quest ll. Small screen, but it works pretty good.
I've used on the VTX for 2yrs.
I attached it to the Handle bars with a ram mount. plugged it into the 12v.
plug in in the front fairing. I hope it is okay I attached 2 photos to show it mounted.
It says it is water resistant and after 2yrs on the other bike I've never had a problem with it.