Ebay item # 221944170808 is a six pack for $7.99 and 4-5 day free shipping. I like those even though they scratch pretty easily, since they are so cheep I can afford to toss them for a buck and a quarter each. Beware of the ones that are flat on the front; I thought I got lucky at a contract job when at the issue counter the lady asked me if I needed any "glasses over glasses". Sure says I since I had to buy my own. I put them on and in less than 20 mins. they had ruined my prescription glasses. The style was "flat" on the front of the glasses and not "oval" like prescriptions.
They matched up and ground buggers on the centers of my lenses rather than matching up with the outside frame. The only good thing was that I had a new prescription in my wallet and in the next week I was purchasing new glasses anyway. Now, because of a coming cataract I use the same in a sunglass, and they are 7-8-10 bucks a pop if you can find them. Good luck.