I've seen these icons in this site: http://www.bijusubhash.com/music-pla...free-download/
that seem to be free.
They look right with RTG, although the author says that they " will suit for dark colored music player theme".
You know you can change that with the MUI prefs, but anyway this is how they look now with my settings:
Converted to 24Bit iff images, attached.
Edit: I think it would be nice if someone could search for a set of better images for the small buttons on the right, square ones.