These are improved versions of the X and Z mounts by Ryan Matthews found at
http://www.thingiverse.com/thing:30253
They no longer requried drilling any holes.
The Z mount uses an existing mounting bolt.
Just remove one or both of the washers.
The X mount uses a T-nut in the side of the T-Slot plate.
Materials and methods

Micro switches
M3 nuts and bolts
Cutting an M3 thread into the holes helps in mounting the switches.

There is a second version of the Z-Endstop holder and a helper part that I used after switching to the smaller USOVO spindel. This spindle no longer has an upper mounting brace, so the micro switch makes contact with the helper that sits on the lower mounting brace and uses the M6 hole for the former upper mounting brace to be fastened to the machine. (The helper is still 7mm too long. I'll change that next week.)