Hands down, one of the best places to look to find new touhou music is Youtube. Plug in "touhou music" or "東方 vocal" into the search. You can also browse around my database. Of course there's always niconico too.
Gensokyo Radio has a sizable database to search and streams Touhou music 24/7. Tune in and listen a while, you'll probably find something you like.
I've found some good stuff on rakuten and noppin in the past.
Here's a custom search I hope someone will find useful.