Like elsewhere, there are places which are packed out and others with tons of space. Depends what you want.
Sai Kung has marinas
and yacht clubs which might be useful for short term.
Aberdeen packed but might find a spot for a month.
Cheung Chau, Lamma Island have spare capacity.
HK has typhoons of course so need to think typhoon refuges - many available.
Weighing it up I would look at Sai Kung or Cheung Chau which is a 40 min ferry
ride from central and good harbour. Need to check with Maritime Depart but don't think you will have a worry.
PM me if you need more detail.