On AliExpress and other places you can find a waterproof 5 inch touch screen with wireless CarPlay for motorcycles - this thing here.
This is my mount for the navigation bar of my Aprilia Tuareg 660.
Two pieces: One gets screwed to the cradle of the CarPlay-unit (it's garmin-like with holes for M3-screws, 38mm and 30mm apart) and holds four M5 hexagon head screws.
The other part is put on from the other side and is fixated with four nuts.
I did print them with 25% infill and no support. They are sturdy enough.
The author marked this model as their own original creation.