Unfortunately, there's not a single cam site with enough cosplay girls to keep up a 24/7 room with always at least one (or better more) girls in cosplay anime/hentai outfit.
You can have one in outfit at times in some site, but except halloween days, it is quite luck to get anyone.
One of the few is Kosplay Kery on chaturbate, so you could link directly to kosplay keri but she's not online always of course:
https://twitter.com/KosplayKeri
http://chaturbate.com/kosplay_keri/
There's a few in myfreecams too, but same story you don't get them online often:
http://profiles.myfreecams.com/SydneyVici0us
By the way I run a cam site and cosplay/anime girls are welcome.