For this endstop you'll need:
* 10-24 threaded rod approx 50mm
* three 10-24 nuts
* five #10 washers
* two 4mm smooth rods approx 31mm
* two 4-40 x .25" screws
* one 4-40 x 0.75" screw and nut
* one stiff spring that will fit over the threaded rod

Print out one of each part. Drill the top part of the adjustment mechanism to exactly 4mm so the rods slide well but are held tightly. Also lubricating the rods with vaseline helps with the movement.

Assemble per the pictures. The 4-40 x 0.25" screws will thread directly into the plastic.

As it is shown, it is capable of 5mm of vertical travel.

The holes for the limit switch are spaced 19mm apart.

Sorry it doesn't look too good in the pictures, I tried printing it way too fast.