Well, for shirt recommendations, I guess you can start by looking higher in this thread. It mentions several sources. Are the ones mentioned here not suitable for some reason?
Also, "graymarket", in my experience, usually means something like a camera with only a local warranty, not valid, for example, outside HK. Do you mean counterfeit? Some of the shops around Granville Road in TST have discounts on genuine designer ties. (I guess they're genuine. I'm not authoritative on this.)
One of my fav places for ties is at the DFS Galleria opposite/in the Langham Hotel next to Ocean Terminal. Great selection and very good prices. Not many HK'ers go to shop there, but actually there are some good finds.