This is a rear bike rack mount which uses a Garmin quarter turn insert.  My rack light mount has two holes 19mm apart and accepts M5 screws.  The M5 hex head screws I used for this came off my previous rear light's mount. 

Required:

1. Garmin quarter turn insert.  33.3mm diameter, screw holes are 3mm and are set 20mm apart, each 10mm from center.
2. 2x M3 hex cap head screws with 6mm long threads. Caps are about 5.5mm wide.
3. 2x M5 hex head screws.  Hex heads are 8mm and threads are 12mm long.

I printed this in PLA at 0.1mm layer height with a 0.4mm nozzle.  I used supports just for the small screw holes.  If I were to do this again I would add a sacrificial layer across the screw hole.

Update:

I added a new version of the model.  The original didn't have enough clearance for my fenders.  The new version moves the radar up by 32.5mm.  I have been using this version for a couple of months now and it works great.  Requirements are the same as the original.