There are lots. Have you seen the little red book 'shopping in shenzhen'? It has a few good suggestions and is a good guide in general. You can get it in Dymocks.
We have recently had some stuff done by Molly at shop Chu Zhi's Tailor Shop number 5072 on level 5 and we were all very happy with the clothes they made. I've gone to other places and had mixed results, but it is always a bit of a gamble. You will definitely get the best results by getting something copied rather than designed.
Remember you can also get them to deliver the clothes to you by courier, it's cheap.