Chaetomorpha isn't really hard to find. There is a person who sells it on that popular auction site, and I know many members here have it as well.
A google search will give you several sources for purchasing it.
Thomas
DON'T buy it from one of those guys on that web site. The one that includes live sand and grape algea. I didn't get what I paid for at all. Check the feedbacks. My name is the same there. I left a negative one. Try one of the other guys.
I may be able to get you some Chaeto, When I prune mine back I just end up throwing it away. You would just have to pay for shipping. If you are intersested, give me your e-mail.