Update for anyone who is interested in buying a dress in HK: I have chosen a dress from Bride and Gown, a shop at 8 Wyndham St. on the 8th floor in Central. They are very nice to work with, and they came recommended by a few of my fiance's coworkers. It's a little pricier than what I hoped, but they are making a completely custom dress, and the quality of the samples is very good. I am saving some dough by purchasing Thai silk fabric from Siriporn on the escalators. She actually has very good fabric for a good price, but she did try to sell me some acrylic and acrylic blend fabrics for the same price as the silk, so be careful. Also, if you opt to buy fabric somewhere else other than the shop where you are having your dress made, be sure to bring a small sample to the dress maker so she can verify that it will work for your dress, and find out the length AND the width of the fabric you need. I came close to getting nailed a few times with the whole fabric thing.
This is the dress I chose:
