Try craigslist - my son was in similar situation several years back.
If you're enrolling in city u of hk (not sure if same as HKU), try this place; my son stayed there for 6 months before he moved into apt and it's 10 minutes to city u:
http://hotel.ywca.org.hk/eng/YWCALod...e_location.htm
Very nice and safe location.