I made this Z End Stop Mount to fit onto my Prusa i3. It is bolted onto the Z stepper motor in order to stop the mount twisting over time and changing the Z home position. I have uploaded it in 30mm and 40mm tall versions to suit your extruder set up. I am using the 40mm mount with a witbox extruder, and the 30mm mount with my E3D V6 lite and custom direct drive extruder.
This is a combination of the Hephestos End Stop Mount and a section of the Z stepper mount. They were combined and trimmed in blender.
I print them with 0.14mm layer height using a 0.4mm Nozzle. 2 perimiters, 0.8mm top/bottom and 20% infill. all at 30mm/sec.
The Z End Stop Mount can be downloaded from thingiverse here.