I found them in Wal Mart and our local grocery store

try Nancy's Notions.

I have plenty of dress making patterns that I have stored for many years. I have a vacume bag sealer gadget it melts the plastic to any size you need, so I use any plastic bag (toilet roll packs have a nice big piece ),Fold the plastic around the pattern envelope, lay it in ,lower the lid of the sealer,in seconds the bag edges are sealed.Leave extra bag on the top and seal there also.
If I use the pattern cut of the top to open the bag, then bend the top down to store in my filling box. My patterns are neat and the envelopes are not ragged and torn from age/use.
The sealer is for kitchen use and not too pricey.
From Bev