An Iwatobi High School Swimming Club Jersey from "Free!"
There are also costumes for male characters! Replicas of the Iwatobi High School swimming club jersey, which appear in Free!, are actually really popular with female cosplayers. They go with nearly anything, are great for group cosplay and are also a nice outfit for summer!
This can easily be worn on top of a t-shirt, or even over a swimsuit! They also stock B holders (a type of corset), which can be something of an essential item for female cosplayers who want to wear male costumes. They can be used to really flatten a woman's bust, giving the impression of a male chest.