I printed the endstop by psbox, but it broke during the install. The problem is, that it was designed really thin, in order to get the switch under the part it needed to hit. I made it more robust by moving the sensor board to the back side, and making the support thicker. Works well for me. I also included a knob that I use as a thumbscrew on the bolt, making it easier to adjust.
I wanted something I could reach easily from the front of the printer, yet strong enough that it wouldn't move on it's own.
Assemble by putting a long M3 bolt through the knob, put a nut above the knob and tighten it down so turning the knob turns the bolt. Then put the bolt through the bottom of the square housing, through a spring (I used a spare bed leveling spring), and through the square block and nut on the sensor mount part, then on out the top. Put a washer and nylock nut on top.