Go for the Medela Symphony, Annerley rents them and they are incredible!
BTW - to save you time, Annerley rents for the same price as the supplier in HK (I already compated prices)
If anybody is looking for the hospital grade Medela electric double breast pumps they can be rented from the physiotherapy clinic in Hutchison House, Central: $1000 for 3 months. Respiration monitors are also available.