Ummmm, Since there are no import tax in HK, I think stuff is cheaper than in the states... I dont remember how much my visor was, but I remember thinking that price was pretty standard... and I dont have a Helmet Bag... sorry!
As for HK, I would recommend MOTOMART in TOKWAWAN in Kowloon. they are like the Road Rider of HongKong. They carry pretty much everything...
As for BJ, and China in general, There is very limited selection and the pricing stinks due to a 20% import tax...
I'd stick to getting stuff in HK...
However, if you are lucky, u may be able to find a FAKE PLEATHER Dainese suit... they are hilarious. I cant imagine going down in a pleather suit thinking it was real leather.