I'm surprised that your quilt shop doesn't have them. I think you can get them on several on line places, like Nancy's Notions, or I Have a Notion, or JoAnn's, maybe even Connecting Threads. I have often used plastic canvas to line the bottom of bags. Someone on here suggested cutting the plastic dividers from the ArtBin Super Satchels, if you have any. Almost any sheet of plastic would work, as long as you can cut it and it seems to be firm enough. Good luck with your search.