I wear bifocals, and have tried the glue-in gauge readers on a set of drop-in corrective lenses. They didn't work because the inserts needed to be glued to a flat surface, and the inside of the lenses was beveled.
I also tried the hydro-tacs, which were better. But they had a tendency to slide around the inside of the mask in warm water. I lost one while rinsing a the mask out, which was the end of that experiment.
Single-vision contacts with a plain glass mask were OK. As the contacts were for distant vision, they ruined my close vision underwater. I also had to carry a pair of reading glasses to see anything close up between dives. The prescription for the reading glasses was different from my normal prescription because it had to compensate for the contact lenses. I didn't have a problem with lenses washing out in pool training or ocean dives, but some people do.
In the end I had a bifocal mask made by Leonard Maggiore Opticians in the United States. I went to my local dive shop,* found a mask that I liked, and then bought the mask from one of the large US retailers and had it drop shipped to Maggiore, who fitted the lenses and shipped the mask to me in Hong Kong. Total cost, about US$350. I was happy with the service and would use Maggiore again.
This isn't perfect—getting the transition point between the near and far parts of the lens in the right place is not easy—but it's the best solution that I've found so far.
LMK if you have questions
* I spent a bunch of money on other things that I needed to compensate the LDS for the use of their showroom.