What I would suggest is first go to your local dollar store, drug store, walmart, etc where you may find a display of cheap reading glasses, then try them on size by size (1.25, 1.5, 1.75, 2 diopter, so on) until you find a couple pairs that let you see and read small print at the focal distance where you approximate your lathe work to be at.... buy those (plus one diopter stronger) - they're fairly cheap most displays (like $8.99 to $12.99 or thereabouts I imagine) and pretty flimsy, but the reason is you want to go through the motions of turning fine details at the lathe with each of the pairs for a half hour or so each and see what feels most comfortable (not fitment wise, but vision/headache wise - squinting for long periods you may find you get headaches after..) Though if you have good vision coverage plan, you could get an actual optometrist/opthalmologist to do the same thing, possibly for less money/co-pay than you'd spend on cheap readers...
Once you find one or two dipoter lenses that work for you, you can go and look up safety glasses (amazon has a huge selection - I got 3M Brand bifocal) with those magnifications desired, and you should be in pretty good shape. I got prescription bifocals myself (aging etc) back in late 2021, and the prescription turned out to have the same diopter magnification as the safety glasses I had been wearing. (My long vision is still 20/20, but can't read normal print up close any more)
Of course, if you find the optivisor comfortable (I have one too and use it sometimes for cutting dovetails on flatwork and similar precision detail) enough to ear all day with face shield/papr then that would work nicely too.