For Hong Kong, the computer malls in Tsim Sha Tsui, (The computer mall, not the cellphone focused one) Mong Kok and Wan Chai have mechanical keyboards for sale. Mostly gaming keyboards, a place in Mong Kok has Duckies and Tsim Sha Tsui has Filcos.
For Topres and other rare stuff, there's a specialist store right beside the Tsim Sha Tsui Computer Mall called Keyboard Hell (If I remember right its across the street in a small walk-in section that is normally filled with Camera equipment). I think its called Keyboard Hell, I posted the exact address some time ago but I forgot it now.