I purchased a pair of slip overs from Wale Apparatus which are rather large, but they really do fit over my prescriptions very well. If you're interested in them, here is a
LINK. I purchased the B3-Series and with the light amount of lamp working I've done at classes and other artists studio, they work very well.
Otherwise, Devardi Glass sells clip-on ones that work pretty well if clipped on over Didymium glasses (Assuming you have a pair on hand from soft glass), linked
HERE. Scroll all the way to the bottom of the page and it's the second from the bottom. I just purchased their soft glass shades from there, since I already have a really nice pair of boro glasses.
Also, if you're interested, you can talk to your optometrist about getting prescription didymium glasses. They can be quite pricey, but we are talking about your eyes here. One of the most important parts of our bodies.