No good mounts that I know of. I use the waterproof smartphone "bag". Tie it, keep it in PFD pocket. Backlight is full brightness. I use it to call the boss and report what time I'll be back, very seldom to check charts
After a few uses they inevitably develop tears around the main opening, so watch for those and replace before they let water in.
I had a Garmin Quatix first gen, was great for rudimentary nav (died recently :-/ ).
Speedpuck for speed / windshifts.
Sometimes thinking of a Garmin 78c but it's old and overpriced. Might get it for a long trip.