Are you sure you want to buy a PG in HK? I was just back from there. Price wise, not so big difference and the box is huge. So, you may not be able to bring it in the plane as hand luggage. and you don't wanna check it in. I guess you could throw the box, and cramp the runners in the hand luggage bag. I wanted to get the GPO1 there, but it was between 1300 to 1600 HKD. So I decided against it. After conversion is like 600 to 800...not much difference.
Anyways, for Gundam shops...best is along Nathan Road...closer to Jordan's MTR station. checkout In's Point and Sino Centre. Also near the Kwong Wah hospital near the station also...many shops there. Paints like Gaia Notes is going for HKD22.00, about RM9.00.
Go there to buy rare stuffs, not easily available here. My opinion, don't buy stuffs there just because it's RM50 cheaper.
I got the 7 eleven zgok HG at around RM80.00, Time machine in Times square sells it at RM200.00.