Shooting glasses.

[BigEars]

I got mine made at the local Spec Savers. I asked first about bringing the pistol in but there was no problem and they offered a tinted option. I had the lens the same day.

[AC99]

Just give your optician the lens holder and he will make you a prescription lens to fit and one that meets your focal length requirements.
When my eyesight began to deteriorate my local optician made a lens to fit my Knobloch frames. Years later when I was having trouble getting a clear image I bought yellow and orange filters (optical quality) which clipped over the lens holder thus providing two additional levels of light reduction/image enhancement but using the same lens - cheaper than buying 3 different lenses!