Makergear M2 Z axis hard end stop
The Makergear M2 has a hard end stop on the X and Y axis, but the Z axis can be commanded to push into the switch and mess up the Z adjustment, this thing clips on to the Z axis guide rod and acts as a stop.
I printed this thing in PLA using .25mm layers at 20% infill (standard settings) on an M2. I ran the STL through Netfab so it is clean and ready to slice. It's 23mm tall for my setup, you may need a taller or shorter version, just scale the Z axis for your application. It easily snaps on the guide rod.