You can only get Stihl parts from a walk in dealer. You can get misc parts like fuel filters, sprockets and so forth at Bailey's. But for restoration or rebuilding, you have to walk into a Stihl dealer.
Bailey's claim they have something like 5000 parts for chainsaws including Stihl, I ahve always wondered if they were very limited to only the parts in their catalog or could they get other Stihl parts on special order.
Please e-mail them with your needs and see what they will reply to you.