You can go to Yuyuan Garden or Shanghai Old Street, I think you can find the stuff there. Remember to bargain with the dealer when buying the staff since most of them would be charged much higher than the amount it worth.

you can try visit

shanghai Shi Liu Pu Fabric Market

it used to be located on Dongjiadu. Now moved to 399 LuJiaBang Rd.

When i was a student i always buy fabric at Dongjiadu. Because it is cheap price for me to get good quality fabric . However must let you know it is better try to ask for discount, especially foreigners.