Chris at safevision.net set me up with stick-on bifocals when I had trouble reading vessel nameplates and such without tilting my head way back. They work great for shooting too. I use a 1.50 power bifocal sticker on the upper inside quadrant of my right lens. It brings the front sight into clear focus for hanguns and rifles. Between range visits I peel it off and put it back in the case. It is applied upside down and the bottom has to be trimmed to fit the profile of the top of your glasses. (It doesn't have to be, but it looks pretty odd otherwise.
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OPTX 20/20 Stick-On Bifocals