I recall seeing one or two music commission threads over the course of the past couple years, but they're always rather short-lived, as there aren't a lot of buyers. It's hard to get across exactly what you want out of a music commission, harder to compose something that seems personal or specific enough to please someone you don't know beyond a few lines on a forum, and probably just as hard to verify that it is, indeed, a new composition rather than something regurgitated from some largely-unexplored crevasse of the internet.