Wandering,

Howdy and welcome to the board! Often times you've got to shop around general bike areas to get what you want. A pretty detailed map guide to the best motorcycle and photographic spots in Chengdu can be found here and I've bought more than a few pair of riding boots at the JinMo Motorcycle Parts and Repair Center:

http://www.carlparker.com/chengdu/

Not sure about Beijing although someone will likely pitch in some info. I'll change the posts title to make it more specific...

CC