Shanghai is a GREAT place to get tailored clothing. My strong recommendation for a great tailor is Dean Ding, whom I have been using since 2006. Dean speaks English and also handles many VIP foreign clients ranging from heads of Microsoft to New York symphonies. I recommend that you email her well in advance to book an appointment and discuss you needs. Email her at Dean_Ding@hotmail.com or text/call at +86 137-9521-2352.
Tell her I recommend you for extra service. Here is her business card: