Maybe you should look in the forums before you start a new post...
A lot of people have bought their's from Milanoo. Usually they fit pretty well, but it seems with everyone's Milanoo Ouran Costume the buttons either fall off or just down right break.
As for me, I'm making my own. You might find used ones in the Marketplace forums or on ebay.
But as I said, just search the Ouran forums. And also look up Ouran Highschool Host Club in the search box. Sometimes the cosplayers say where they got their costume or how they made it. Actually, the more I think about it, this is just a basic concept for any costume. Good luck.