J-List
http://www.jlist.com/
Giant Robot (maybe)
http://secure.giantrobot.com/store.php?catid=A003#
Sanrio
http://www.sanrio.com/
UFO Catchers
http://www.ufocatcher.com/
Viz:
http://store.viz.com/
If you're near NJ, try visiting Mitsuwa Marketplace.
http://www.mitsuwanj.com/en/index.htm
Otherwise I'd say try visiting the next comicbook or anime convention that comes your way.