I looked for a GPS mount to buy or print and ended up making my own. It's 2 parts for easy printing that I epoxied together to form a clip into place mount that keeps the GPS out of sight and still easy to see. A nice snap into place indicates a good snug fit. I lightly sanded the ball to knock off any rough edges and it fits the Garmin mount socket nicely.
Lightly sand off any imperfections on the ball surface. Don't worry about any unevenness, just knock off the external roughness from the print where the ball rotates in the GPS socket.