lianluo,
it depends on what quality level you're looking for. If you want good quality at a very good price, pls pm me and I'll give you the name of my friend who is a very reputable jeweler. If you want ok quality for cheap price, there are a couple of places in the basement of the bldg across the street from Central World Plaza (I think it's called Narayana Phand bldg). They can also do stringing there. Objective: to pay the price commensurate with the quality. Even though there are a lot of places selling pearls cheaply, you might still be ripped off because the quality is very low.

Do you have a price range in mind ?