As I know, there is an excellent Qipao tailor named Silk King in Huaihai Zhonglu Road in Shanghai. You may have a try there. His work is excellent and you can get the clothes within 3 days. The cost may be CNY500-1000 Yuan according to the cloth you choose. I don’t know much about that in HongKong, and you may consult your local guide or the hotel stuff for some advice. Good Luck.