there are several important suppliers .
if you live near philadelphia/media i can suggest the sporting gentleman .
there are two suppliers out of state i like,one is joe fox /dette trout flies in the catskills .
another is jim slattery,he has a site but i get it from him on ebay.
my number one source of materials other than those stated above is feather craft in saint louis.they have a great catalog and do traditional mail order
http://www.feather-craft.com/
good luck!!
PS also,sandfly on here has a fly shop.he still has traditional cotton chenille!
if someone could post a link