I would recommend on-line HK tailors for shirts (Not a Suit as you must get fittings) if you are only in town for a short time. Order them before you take off and get them delivered to your hotel for when your arrive.
A list of on-line HK shirt makers
www.cottonwork.com - huge choice of High-end fabric
www.nialma.com - simple to use site
www.lewistaylorshirts.com - easy to use site with good brands of fabric
www.moderntailor.com - 2000 fabrics
www.itailor.com - Site seems to be down at the moment
The main differences are the types of fabric super 100's and up are good super 140 and up are great but wrinkle, the types of button (Shell or plastic) and the quality of the tailoring.