I understand Ryan's hesitation. There are lots of material sources, and retailing the stuff is a thankless job, and it would be hard to keep up with a changing market of specialized materials.
There is another way to go.
Why not have a sourcing department on the website -- a clearinghouse for sources of fabric, hardware, etc. from reader suggestions and adjusted for reader feedback - a'la Amazon or EBay. Divide it into categories: fabric, thread, narrow goods, plastic hardware, metal, general hardware, adhesives, treatments, tools, etc.