A while ago I modified a circular fan duct for and mount created by mcleishn, the modified version had an improved duct that was easier to print and a mount for an 12mm inductive sensor.
I have improved my original design by making the base completely solid and adding a lip to the left to prevent mount from bending during movement. I also made the sensor mount one solid part with a M3 nut sized hole which prevents lose. And finally, and most importantly I made two versions with different diameters for both 10mm and 18mm sensors.
I am happy to modify this design for other diameters if anyone needs it.
You can read a full blog post about this https://mkdev.co.uk/improved-inductive-sensor-support-hictop-prusa-i3/