As promised, the Club Penguin Song The Party Starts Now is for sale on several different services including iTunes, Amazon MP3, and Google Play. The song costs $1.29 (in United States Currency) on iTunes and Google Play but costs $0.99 on Amazon MP3.
Here are the links to the song on the different services:
You can also get the song free from Amazon (only for United States residents only) by redeeming $2 credit here.
The Party Starts Now is also a ringtone on the iTunes store and costs the same exact price. The ringtone has been for sale for roughly a week and a half already. Have you gone ahead and purchased the song?