Where can I get Mark Mancina's "Washington Square" without downloading the whole album?

I was watching August Rush the other day and I really liked the music. One song in the movie that I particularly liked was Mark Mancina's "Washington Square", the one played after Lyla and Louise spend the night together and he asks her to meet him by the Arch. I got the album off Itunes but that song wasn't on the list. I knew the song's name because of the subtitles I had downloaded earlier. I would really love it if someone gave me a link to download the song from, preferably for free because I paid $9.99 for an album when I only wanted one song. PLEASE HELP.