This is a new X endstop that mounts on the left side to the X-axis rails. It is designed to contact the X-axis extruder carriage.
I started with this: http://www.thingiverse.com/thing:1037870 and added a higher mount so that it works with the Folger Tech 2020 Prusa i3.
X_Endstop_Folger_2020.stl | 229.1KB |