If you are handy with 3D modeling, you design a custom mount and have it printed. Even if not, it is not too too hard.
The software to model is free (fusion 360 is free for a year for hobbyists) and printing it out would just cost you shipping...just send me the file!
I'd imagine the easiest would be zip tie mounting a crossbar that would nestle perfectly between your bars. You would then glue a garmin mount to that. A little fancier would include a garmin mount in the print. Fanciest would wrap around the bars and screw clamp.
Edit: https://www.thingiverse.com/thing:292539 That is a pretty easy piece to modify to match whatever your bar spacing needs to be.
The software to model is free (fusion 360 is free for a year for hobbyists) and printing it out would just cost you shipping...just send me the file!
I'd imagine the easiest would be zip tie mounting a crossbar that would nestle perfectly between your bars. You would then glue a garmin mount to that. A little fancier would include a garmin mount in the print. Fanciest would wrap around the bars and screw clamp.
Edit: https://www.thingiverse.com/thing:292539 That is a pretty easy piece to modify to match whatever your bar spacing needs to be.