Jo-Anne's is a huge store in CA that sells a good selection of fabric (especially the Joanne superstores)and tons of cool crafts supplies like a MIchael's. I'm not sure if they have it outside of CA. They sell online too but I can't imagine buying fabric online seeing that I have to touch and feel to see if the quality is good and what the washing instructions are. But if you don't mind, I've seen good old ebay carry fabric as well. Not sure where you reside, but here's their link, you can do a store search
http://www.joann.com/