I liked very much jimustanguitar's micro z-probe so I designed one for the regular size microswitch. I prefer to that one on heated bed since it has a tiny lever.
You can see both compared on the images.
Besides the holes for the microswitch, I changed the orientation because i this orientation doesn't need any support structure, and there is no bridges
There is also a tiny notch on the side that accommodates a screw head (which is protruding a bit over the edge)
Designed in SketchUp.
Do not use with heated extruder - obviously.