Here are 3 suggestions:
SHOOTERS LINKS
Decot Hy-Wyd
www.sportglasses.com
Morgan Optical
www.morganoptical.net
Lehman Optical
www.lehmanoptical.com
I had shooting glasses made by Lehman Optical. Send him your prescription and he adjusts the prescription to focus on the front sight or at some point between the front sight, and a target located at a distance of your choosing. Measure the distance from your eye to the front sight. He also wants to know the distance between pupils. Best to discuss this with him by phone. I also had reading bifocals made on the lenses. Before the shooting glasses I tried on drug store reading glasses until I found the right strength, but this was not satisfactory because I had to wear shooting glasses over the reading glasses.
Lehman also made me some trifocals I used for flying so I could focus on maps & charts, read the instruments, and see the runway. Before that I was juggling two pairs of cheap reading glasses for in the cockpit, but could still see distance OK. Finally had to give up the flying due to age and high blood pressure. Still enjoy shooting, but one of these days I'll have to have cataract surgury, and get new shooting glasses from Lehman again. Some days I feel like Mr. Magoo.