Best shop in shanghai: take a taxi to pudong airport, buy a ticket to Bangkok ;-)

Believe it or not, im being serious, especially if your shoe size is bigger than a childs. For what you'd spend getting ripped off at Chinese shops you can afford the ticket easily and have some good food in the bargain.

There are three HUGE shops in BKK - Dainese has a giant showroom there, Panda riders is great and the Stockade also has a ton of stuff.

That said, there is a shop with a decent selection of clothes and stuff in putuo: jiaotong Lu and Jiaoji Lu. The whole street is bike stuff, but I couldn't say how "authentic" it is and prices are pretty steep for the Alpinestars, Arai, Dainese stuff.