Agreed about pet shop puppies - they are often unhealthy and almost always come from breeding farms.
Contact the Hong Kong Kennel Club for possible details of a local breeder.
Hong Kong Kennel Club
If you find a breeder (even if recommended through a kennel club) you should still visit the premises to make sure it is clean and the dogs look healthy.
Alternately, you can contact Hong Kong Dog Rescue, which frequently gets young (one year or less) purebred pugs which have been purchased and discarded. With a slightly older puppy you run a much decreased risk of getting a sick little dog.
Hong Kong Dog Rescue