Broom;
Simple solution, find an optometrist who is gun friendly. Take a weapon or two (rifle, hand gun) in for an exam, have him average the focal distance to the front sight (mine is 39"). Have your shooting glasses ground with normal distance Rx in non shooting eye & whatever he comes up with for focal distance in shooting eye. There will be a period of adjustment, but soon your brain will simply adjust to the glasses.
Ive been doing this for years, for shooting purposes my 66 year old eyes see the sights like 20 year old eyes.
Hope this helps.
BTW, I'm not sure the Knobloch glasses will fulfill the safety glasses requirement.