There have been several threads on the suit topic already so a search is worthwhile. However, to give you my personal experience (I used to live in SZ)...
On the 5th floor of the Luohu (Lowu in Cantonese) Commercial Centre is where there is a concentration of tailors. The Centre is the first place you come to if you cross from HK to SZ at Luohu, everyone knows it. A lot of these are actually branches of HK tailors. There are also a number of stores where you can just buy material and take it to a tailor for making up.

Tai Cheong Tailors was recommended to me when I lived there and I ended up buying 3 suits from them. It works in the usual way for a bespoke suit; loads od swatch books, choose material and a style (often a good idea to bring in a suit if you want the style copying). They will then do an intial measuring and then give you a piece of the swatch. You can use this later to make sure the material the suit is actually made from is the same

They will offer one more fitting in around 3-5 days, followed by the final fitting a further 3-5 days. Bearing in mind you may not have that much time I would have thought a negotiation could be had where you can trade-off the price a little for a fast turnaround

The costs are entirely dependent on what material you choose. Cheapest wool suits in 2007 were about RMB700, most expensive Cashmere suits were about RMB2300. I went for Wool/Cashmere blends which worked out at RMB2200 with an extra pair of trousers and they have been excellent

There are plenty of toys in the Centre on the lower floors (plus all manner of other goods, some dodgy fakes, some not) so I suggest you look there.

nickyboy