http://www.ebay.com/
http://www.cgboxing.com/
http://www.boxingwholesale.com/
http://www.fightsondvd.com/
http://www.boxingdvd.com/
http://www.boxinggalore.com/
http://www.boxingcraze.com/
http://www.wcboxingsource.com/

ask google as well, I'm pretty sure there are plenty sites for your goal