dolawren - RealTracks is only a site that has links. The only store selling digital copies in Canada is PureTracks. (www.puretracks.com) Their music uses WMA9 (*cough* Avoid like the black plague *cough*) and tracks sell for anywhere from 0.99 to 1.19 if I remember right.
Heh... I gambled $0.99 and switched my user agent in Safari (via the 'hidden" Debug menu) to IE6.0/Win to get on their site and buy a song. It downloaded okay, but I had to finagle the download -- and I can't remember how. The STUOPID thing about it, was that the nice shiny brand new version of MS Winows media player for OS X CAN;T PLAY IT! That's the same experience I've had with several WMP files I've tried on this BRAND NEW version of the app.