"Buy Now" links in popular media players with PAD/Metadata

I work for a radio station that broadcasts streams online with RTMP, mp3, AAC+, and some other stuff. We're going to start including Primary and Secondary PAD/Metadata so that everyone's player can display the song title and artist name. As part of the Secondary PAD/Metadata, I understand that I should be able to include metadata that popular players will pick up on and display as "Buy Now" links for the iTunes store. Here is some of the only documentation I've found on the subject, and it is largely silent on the details, stating simply that, "Such features as additional information about the content, album, year, graphics, or even buy now links can be included."

Does anybody know what information to place in the Secondary PAD/Metadata to cause any of the media players to display an iTunes store "Buy Now" link? Here is an example link for a song one of our streams played today:

http://click.linksynergy.com/fs-bin/stat?id=JdrK1p6r8Mw&offerid开发者_如何学Go=78941&type=3&subid=0&tmpid=1826&RD_PARM1=http%253A%252F%252Fitunes.apple.com%252Fus%252Falbum%252Fa-german-requiem-op-45-denn%252Fid105607338%253Fi%253D105606523%2526uo%253D4%2526partnerId%253D30