Garmin quarter turn mount for your own designs. This is the “minimum” required to make some custom mounting option. Feel free to add this mount base in your project.
Mount comes in two different variants. First the “original” looking one, it flexes too much with PETG though, so I designed another variant with less flex. I recommend this one if you don't have some sturdier filament.

Printing tips
It is slight difficult to print perfect with PETG. Without supports you might get some extra material, just cut away with a hobby knife. Be sure to remove all excess material so you don't damage you bike computer!
Have tried printing with support also but that was not so much better, removing the supports damages the flange also. So just print it without support, I find it best.
Check out my Garmin Gizmos collection for other related designs:
https://www.printables.com/@BentDerailleur/collections/2063450
If you like my work, consider buying me a coffee:
https://ko-fi.com/maildannesholkse
The author marked this model as their own original creation.