If you go to pricegrabber.com and search for "Visual Basic 6" under Software, you will get a list of places to get it. Yes, the list is getting small with the release of vb.net. Here is a link to one of the sellers:
you might want to try checking out ebay. sometimes there are copies of VB6 in new sealed boxes for decent prices. just make sure, if you are going to bid on a copy, that it is not the educational version.