Most knife catalogs I get in the mail seem to have a variety of, usually, cheap Katana's/ "NinjaSwords" etc. Smokey Mountain Knife Work's catalog usually lists a variety. For more serious/higher quality swords, companies like CAS Iberia at
http://casiberia.com supposedly make very good ones. Also a company called The Sword Amory at
http://www.swordarmory.com list models from $297 to $929. An internet search using the terms martial arts or just katana will, I'm sure. give you a lot of other sources.