There's a shop in Peace Plaza that sells bikes and biker gear. It's on the first floor, by the Kingston department store.
I wasn't too happy with their selection though. They were too brightly colored for my taste, and some came with rainbow tint.. yechh.
Now this pair I'm wearing on the picture, if that suits your taste better, I got from a dealer in Beijing. It comes with a leather helmet, and including delivery to Dalian, it came to about 130 RMB.

I can give you his information if you like. He accepts paypal.