At Amazon I bought Elvex RX500 Full Lens .75 Magnification Ballistic Rated Safety Glasses to help my 70-year-old eyes. The .75 is half of what I use for reading glasses (1.50 diopter).
They are full lens, not bi-focals. I can see the target well enough and the front sight clearly. Now these are my go-to shooting glasses for pistols.
I have also adopted full lens magnification safety glasses for shooting handguns and iron sighted rifles. (Also, for working in my shop although I have a stronger magnification level for the close work).
There are some companies out there that are making shooting glasses with the bifocal cut in the top of the lens instead of the bottom. I have not tried them yet.
If the OP has not done so recently, I'd get checked for cataracts. Until I had cataract surgery a few years ago, the sights were getting more and more difficult to see due to the clouding of the lenses in my eyes. The surgery replaced the clouded lenses with clear implants and I can see much better now, even distance vision without glasses. It does usher in a different set of needs for corrective glasses for near vision though.