I designed this for my Neoteck DTI Electronic Digital Dial Indicator. Other brands should work too. It is best printed without supports with the front side down. I printed mine with a 0.6mm nozzle with three perimeters and a 15% infill.  For 0.4mm nozzles, increase to 4 perimeters.

You need to detach the 2 part fans and use slightly longer M3 screws. You also need an M3x20 and a square nut for the clamp.