Go to Chinatown. Many shops and traditional clothing store's down there. You caould also do a walking tour which is pretty cool.
The link for the walking tour below. On the same link there is a visitors number that you can call, and maybe they can streer you in the right direction for the costume shop.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.