I use DeCot Hy Wyd - out of Arizona... for my prescription lenses for shooting...
http://sportglasses.com/
You have to have your eye doctor ...get a couple of other measurements for them ...but its easy / no big deal. Once you buy the frames...then you can order different lenses as needed. They've specialized in shooters glasses for a long time.
If that is not in your budget....get your prescription ...go to Costco or someplace...and they can make up shooting glasses.