They can be purchased new from any dealer. My favorite online places are Ronayers.com or Bikebandit.com, both of which usually beat the local dealer's prices.
The 2006 C50T saddlebags are part numbers 3651577-001 and 3651578-001, but you'll have to call a dealer and see which one is the left and which the right. The bad news is that even online they are $370 each.
For that price you might be better off getting a pair of aftermarket bags. For example, Custom World International Rigid Bags for your bike are only $370 a pair with mounting brakets. Or for about $450 you can get a pair of Leatherlyke hard bags that are waterproof and lock. Or if you want to stick with semi-rigid soft bags, a set of Saddleman Cruis'n Jumbo Slant Bags is only $125 a pair, and River Road Zip-off Extra-larger Classic Slant Bags are only $150 a pair.