The Medela pumps are excellent. I had a single electric pump which worked really well as I pumped 2X a day. If you're planning on pumping more often you might want to consider getting the double Pump in Style.
You can purchase limited selection of these pumps at Eugene Club , Mannings, and Wing On or you can go to Celki Home Health Care Centre where they have pretty well every Medela product.
The one rani recommend cost HK$ 690.00. There is actually a sale on at Wing On right now, 10% off all baby products including beast pumps.
This has one advantage over the electric pumps - it doesn't make the noise an electric pump makes - this could be important depending where you will be pumping.