You can find accessory stores in almost every shopping mall and major shopping area both tourist and local area.

There is a big market for stuff off subway Line 2 at the Shanghai Science and Technology Museum stop. They sell everything there, cloths, luggage, watches, glasses, tailored clothes and electronic goods. Must negotiate, whatever they offer, cut it by 1/4 and if you pay more than 1/3 you've paid too much, LOL