I really liked this original fan mounting design, it is so simple and requires so little hardware. However, I found that the angle of the fan was not easy to adjust, and the default didn't work for me. So, I made the same part in openSCAD and made it possible to change the fan angle. The original part was 0 degrees, and my default version is 45 degrees.
Print and clip on like the picture!
If needed, adjust the fan_angle variable at the top of the scad script, and print a new version for yourself.