I wanted to mount my GPS navigator directly to the mirror mount. I had something fancy in mind, but then came up with this simple solution which can be used generally.
For fixing the Garmin 61 I use parts from this design https://www.thingiverse.com/thing:1715919
I then have two of my parts to get 2 axle movement. There are 3 holes to get maximum usage options.
The first part doesn't allow free rotation. I rasped away some material to use it. For that reason and for strength 100% infill is helpfull. Otherwise a lower value will be fine.
The second design is fixed for these problems but I didn't print it, yet.
Infill depending on strength needed.