I avoid using agents. I recently had a bad experience with a landlord and ended up losing my deposit and two weeks rent and the agent did zilch.
I subsequently found a private landlord, drew up a contract with her from a template, tweaked a few terms to our mutual satisfaction over some coffee (which I paid for), signed it and moved in. Total cost about HKD 100 and a couple of hours of my time on a Sunday.
I read with a certain sense of schadenfreude yesterday that estate agents in the UK were laying off staff due to the recent housing slowdown. I tried not to cry.
I tend to agree with Jimbo's last comment. Take a Chinese speaker with you to negotiate with the landlord and agree the terms of the new contract. If you were both happy with the terms of the last contract then simply draw a similar one up (changing anything you agree on mutually). The landlord will normally have to pay the agent as well so this could work out better for the landlord.
Presumably the landlord trusts you as she would not wish to keep you as a tenant so it should not be too much of a problem.