You can get the Qsim in Sham Shui Po. Take the exit for Apilu (spelling?) street, opposite from the computer centre. I believe exit C. When you get topside, go diagonally right across the intersection to the first telephone repair stand. They should have it and installed it for me for 250 hkd if I recall correctly.
This device gives you 3 sim card capability.
Cheers,
Soda