Phase Blocks for 1-1/4"(31.75mm), 3/4"(19.05mm).
Will take screws: 10-24nc or M5. Holes are near size but will need drill chasing and tap.
Recommend print with PET. 50% Infill seems to work well. Not meant to hold work for miter cuts. But if you're daring, maybe 100% infill can hold work?
Pithy Bikes Phase Blocks are free for use but not for re-sale.