Buying cosplays online

What is a good website for me to buy cosplays? I want to get a Yuuri Katsuki cosplay so I can use it when ever I teach My girlfriend Okami to Ice-skate. She really wants to learn how to roller-skate, but I thought since I want to ice-skate again, and she wants to roller-skate, it'll be a great idea to take her ice-skating, since there's really no difference between the two.