I'm not sure about the 3HK card, but Fortress sells a card based on 3HK for HK$138/month which gives 3GB worldwide, 4GB in Asia, 10GB in UK/US/Aus/NZ/Can, or 15GB in China/HK/Macau.

But that limit is just for high-speed data. It is completely unlimited data at 128kbps, which works fine for me - I can do browsing, messaging, voice calls, and (basic quality) video calls within that, which covers everything I'm likely to want to do when moving around without access to WiFi.