You don't need different IPDs if your visor has prism. Prism lets your eyes point straight ahead focused at infinity, with the lenses supplying focusing, and the prism, vergence.
The combination creates the illusion of staring straight into the distance--fully relaxing your eyes' extra-ocular and ciliary muscles-- even though you're looking at something close-up.
Without prism, external lenses upset your vergence/accommodation lookup-table assumptions, resulting in simultaneous urges to converge & diverge. Your lateral and medial extra-ocular muscles then both contract, clashing, and the end result is eyestrain / fatigue. Prism eliminates that.
These guys make the OptiVisor, which uses a prismatic lens:
I've never used a stereo microscope. That might be as good or better, with longer working distance, but the OptiVisor sure is handy and, at about $35, not terribly expensive.
The tilting up and down when you need to look around them is a bit of a pain, but the overall utility is fabulous. I love mine.
Cheers, James Arthur