I recommend checking out http://www.taobao.com and search for the brands or designs that you’re interested in. Keep in mind you’re navigating a landscape of many fakes but once you find a seller that deals in quality you’re comfortable with, stick with them. That’s what I do, at least and it’s worked out pretty well so far.
What I find with a lot of the shops in Chengdu is they either have goofy looking clothes or they have nice threads that cost far more than what they’d cost in the US (after they’ve been shipped there from China, undoubtedly changing hands a few times beforehand).