Where to buy high quality copies of top brands in Beijing?

heloo everyone
I'm visiting beijing first time.. my goal is clothers business, the high quality copies of top brands (mqueen, alexander wang, marc jacobs, ice berg, westwood, and ext)
in low prices. i have seen yabalu areas, silk market, yashow market.. on the top is yabalu but steel hope to find better place, for better quality and cheaper as it is business.. can someone give me a hand and tell where to go else?? thanks