I have a bunch of UGC's that are pre-cut to fit NES carts. These have been modified using side cutters so its not the prettiest job in the world but it works. 

These are used, some of them have slight tearing on the sleeve corners, which are very fragile to begin with. 

Prices are shipped

9 for $13 x1 available
16 for $20 x3 available
Yes you can get them cheaper if you want to wait for media shelving, but if you just want a small amount and dont want to cut them yourself then this might be a better deal.