If you need to buy an older version of Crystal Reports, all the way back to v8.5, you can now download them directly from BO (for $595). This link includes all versions from 8.5 forward.
If you want to save a few bucks you can check on Ebay, where I regularly find older versions for sale. Just make sure you know what you are purchasing. In 2002 I wrote an article about what to look for when buying CR on Ebay. That article still applies, although some of the product codes listed might be different in newer versions.
Or check with me. I sometimes know of extra copies that are available.