I found a pretty good site for a company in new york called Action Toys and Collectables. Some of their stuff might be a bit pricey but it also looks like they have dome good deals, I guess it all depends on what you are looking (or desperate) for. Here is a link to the 2k3 section
http://www.actiontoys.com/Merchant2/..._Code=TMNT2003
There is alot of vintage stuff on there too, take a look.