Plenty of them, especially at TST, around Holiday Villa Hotels, Nathan Road. Indeed, you can find a few preowned shops at the basement there. If those shops cant satisfy your requirement, walk a few blocks to hotel mira, opposite hotel mira, there is a building full of pre owned shops. Most of the shops are alright reliable I will say.
Also, there are a few of them at Shun Wo Center at Mongkok, Nathan Road. Most of them are alright too. Very competitive. Guess its just a matter of which one offering better price. Rolex in HK is generally cheaper than Msia.