I'll bet a lot of bigger thrift shops just "rag" fabric pieces, that is , toss it in the bins where they put damaged clothes (then are sold to manufacturers or third world countries). I wonder if talking to the manager of your local shop about the desire for fabric scraps and asking them to set them aside for you to purchase would work. I think I will try that here. I have been amazed at what they toss and what they keep. I once saw the local shop filling a dump truck with items that had been left outside the shop when it was closed. Some of them had gotten wet..but they even tossed in plastic items and skiis!