Last time I checked, I haven't heard of any Continental Extreme Contact DW in HK, but that was awhile ago, so don't know about the siutation now. You can consider Michelin PSS as an alternative.
There are several tire shops at Tai Hang, the biggest is called Shing Tak:
http://www.shingtaktyre.com/co_model.asp?type=tyre&id=1
I bought my Goodyear Eagle F1 Asymmetric at this shop at Fortress Hill/Tin Hau, but forgot the name, the folks here recommended it to me, it's on Watson Road.