fivewits wigs is an in US wig store and they do have character wigs. Cosplay fu is outside the US(I think) but I've heard good things! CosplayWigsUSA also is a wig company here in the US, and they have a good amount of character wigs.
That's about all I can think of!
Next Convention: Anime Detour
Peko Pekoyama- Super Dangan Ronpa 2(95%)
Kiryuin Satsuki- Kill La Kill(95%)
Tycho Science- Diebuster