It is not too hard to find loose angora goat. Mike Hogue has it at http://www.eflytyer.com. If you search around fiber crafts, you can find it for spinning and knitting. I bought a roving (bunch of angora goat ready for spinning into yarn) off ebay a few years ago for about $20 and it is a lifetime supply, takes dye very nicely and ties up awesome leeches. The latest tying craze is to mix some finely shredded mylar flash material with angora goat. Here is a link to a leech pattern tied with it right here on FAOL http://www.flyanglersonline.com/flyt...00200fotw.html
The bearlodge angler (an FAOL sponsor) stocks Arizona simi-seal. The Stalcup's Sparkle Leech dubbing on eflytyer is essentially the same material in different color combinations. If you want a similar material with even longer fibers, try to find some llama. That is a bit harder to find but it is a cool tying material too.