I know who's good for wigs on ebay:
zhenna or "designer wigs and color wigs" they are soooo awesome! everything is kenokalen (sp?) fiber and very affordable! I've gotten two wigs from them and they are outstanding!
But for costumes, just beware, there's a bunch of people who steal images so you don't know what you're really getting. Kairi looks relatively easy, I'd go to Goodwill and find stuff that you can alter easy. it'll be alot cheaper too!
If you really want to buy something, just check around here first for the names of the companies to make sure that they won't screw you.
Morrigan - Darkstalkers
Sailor Neptune - Sailor Moon
Carmilla - Vampire Hunter D
Haydee - Gankutsuou: The Count of Monte Cristo
Barioth Blademaster - Monster Hunter
For Prop Commissions visit my store, DistinctiveProps, on etsy.