The Prusa Z-Rod Constraint is a wonderful thing but its lacking a decent endstop mount. There is another derivative with an endstop mount on thingiverse but we found we broke it too easily or ruined endstops by accidentally getting glue in it.
I have added a supportless version (rev2) of the endstop mount that has elongated screw holes so you can make your adjustments at the endstop and not by moving the z constraint along the rod.
The original enstop mount will need to be printed with support.
You will need:
2 x M3-14 Screws (will need shorter with rev2)
2 x M3 Hex Nuts (the tiny ones about 5mm big)
2 x M3 Washers (Optional)
1 x M4-20 Screw
2x M4 Washers
1x M4 Nut
1 x endstop
1 x 608 skate bearing
You will probably have to drill out the mounting holes on the endstop with a dremel to get the m3 screws thru the end stop.