The Smithsonian Collection CDs are pretty generally available at your local book shops - Barnes or Borders are the largest in my area, although they're not "fast movers" so may not be in local stock.

Check the CD for an ISBN number (some have them, some don't), and/or record number, and it can probably be ordered in fairly quickly.

Or try Barnes (bn.com) or Borders (borders.com) or Amazon on the web?

John