https://www.thingiverse.com/thing:1425181 by OpenSourceClassroom is the inventor of this tool. I needed to modify it to fit my Mitutoyo dial indicator, and also added some threads both in the rodBracket and the DialBracket. For threads I used the FreeCad workbench ThreadProfiles and, M8x1.25, changed the thread angle from 60 to 45 degrees and expanded the major diameter to 7.40.
I didn't use the original base, but merely welded a nut onto a steel plate, see picture.
Works like a charm for me.
Please feel free to modify and remix.