Also, if you happen to have that song on a CD, you can make your own ringtone using a ringtone maker. I used a program that you can download from the web called Audacity to make all of my ringtones.
Easiest way I know to do it is to use phonezoo.com and upload the mp3 to the site. Then you select up to 30 seconds of the song you want to make into the ringtone. The site will convert it and send it to your phone for free.