This is a great thread and having done mass toy hunting trips over there a few times in the last couple of years I agree with Bladestorm, unfortunately In's Point has a lot of KO MP's now being sold at original prices, and Original G1 items have skyrocketed.
One place I found and would recommend beyond anything else is Toyzone, it is on HD's guide but is a ripper (hard) to find when you see the front of what looks like (is) an industrial high rise.
They deal in all things awesome, lots of second hand toys, biiiig section of Transformers from all era's. Plenty of 3p stuff and much much more. And!! (there's more) as was my case I had already filled my bags with other TF buys I asked if they could send it home to Aus, no worries, they boxed it up for me there and I paid the postage price with the purchase. They were really helpful and you could tell they were people who loved their job.
The address is:
Flat B, 4th floor Wah Ha Factory Building, 8 Shipyard Lane, Quarry Bay. The nearest MTR is Tai Koo exit A1.
Bladestorm I'm heading over later in the year so might be good to have a catch up.