Limited time. I'd go look in a department store. Most cups&bowls sections will have some sets to chose from, probably starting from pretty cheap to silly expensive.
I am not local to Shanghai, so cannot give a specific suggestion.

Any good Tea shop

Alternatively, wait until you are in the duty-free in the airport on your way home

Be sure to bargain as much as you can if there is no price displayed, otherwise they will see you coming

good luck

I went to a factory outlet in Xi'an, I bought 2 nice sets, they've been sitting in the original boxes for years.

There are stores like our Dollar stores that sell many different little tea cups cheap and cheap tea sets, but the tea sets aren't porcelain.

 If you have limited time, I would recommend shopping online. Checkout www.craftbro.com, you may find what you want there.

http://www.timeoutshanghai.com/venue/Shops__Services-Markets/715/Nanjing...

10am-10pm daily

Metro Nanjing Xi Lu

English address 580 Nanjing Xi Lu, near Chengdu Bei Lu, Jingan district

Chinese address 静安区南京西路580号, 近成都北路