I think I've posted on this before,
you can go to the Labour Department's website and register and then search for local domestic helpers. One of the search criteria is language.

http://www.jobs.gov.hk/eng/default.aspx

After you register, choose "select candidates" and then fill in what you are looking for.

There are a fair number of women from mainland China in HK who speak Mandarin and are looking for work as part-time and full-time helpers.