Amazon.com: OPTX 20/20 Stick-On Bifocals, +1.75: Health & Personal Care
This site shows them available up to +3.00; I'm still using +1.5.
I use the el-cheapo stick-ons and have had NO problems with adhesion provided that I apply them correctly. Which is EASY. Wash and dry the mask, making sure you don't touch the inside of the mask with your oily fingers when you're done. Use a grease pencil or crayon to mark the OUTSIDE of the mask for where you want the lenses positioned. Use a few drops of distilled water on the lenses and position them according to your markings. Let dry, then remove the grease marking from the outside. I can even wash my mask with de-fog or spit and I've never had them come off until I peeled them.
BUT. Be advised that they have a flat side and a convex side. If you don't place them with the flat side down, they don't stick well (and sometimes not at all).
Cheap is the way to go if presbyopia is your only problem. I'm 46. (That's 42 with 4 years' experience)