Visit the Karaoke, Karaoke Haven or Karaoke Version website (see References). Locate the search field on the left side of the home page and type in the name of the song you're looking for, then press enter. A list will appear with purchasing options for that song. It will display all compilation CDs the song is on, if the song is available for individual download and what formats it comes in, for example CD or MP3. Choose the option you want and click "Add to Cart." The website will walk you through the check-out process.
If you can't find a karaoke version of the song you want, visit the Make-Your-Own-Karaoke website (See Reference 2). This website offers software that will strip the vocals from any song. The purchasing options are available at the bottom of the home page. Choose the correct version for your computer, Windows or Mac OS, then decide if you want to download the software directly or have a CD shipped to you.
Call or visit your local music store to see what karaoke CDs it carries. You may find the song you're looking for, but be aware that this is a more time-consuming process than the other search options.