Hi Micropteris!
Most fly shops sell a product called "Sculpin Wool". I'm not sure if it is 100% wool or if it matters. You can buy 100% virgin wool in several colors from a store that specializes in yarns and such. In my search for wool, I found that the stores like Walmart, Joann's, Target, Kmart and most of the craft stores do not have 100% virgin wool. I was looking for wool for some old European patterns. I guesss in answer to your question, the sculpin wool product is probably what you are looking for. On another note, I was watching Scott Sanchez demonstrate some tying techniques a couple weeks ago where he was tying on clumps of wool/yarn around the hook shank and, trimming top and bottom to give a wide, flat profile, similiar to a sculpin. It was a neat idea and looked good. You can mix-n-match different colors (i.e; brown, tan, olive and etc.) to get a mottled effect. Anyway, I would look for the "Sculpin Wool". My local Sportsman's Warehouse has it as well as a few of the fly shops. Hope this helps.
Bob