I have really been into macro photography lately and am wanting to sell some of the prints in my store. I am thinking of turning them into greeting cards. I was wondering if anyone knew what the plastic envelopes that seal up to store the cards in are called? I have been looking at different art supply stores and cannot find them. I wonder if it's because I don't know what they are called? Also, do you know of a good art supply store online where I could get them at a good deal? Thank you.