reei,
I got my Medela Pump In Style at Bumps to Babes in Central. I bought it last year for HKD4,200. You can also rent Medela pumps (electric, double pumps) from Celki. There is a Celki at Melbourne Plaza (10th Floor) in Central. They also have stores in other places in HK Island, Kowloon and New Territories.
IMHO, hydrating yourself and getting plenty of rest is paramount. It's hard, when you have to take care of a newborn. Don't get stressed out if you don't have a lot of milk initially. That will only make things worst! In fact, if you decide to pump, you will find that the more calm and relaxed (this is a big challenge for new mothers!) you are, the easier the letdown.
Nonetheless, my advice is - don't worry. Cross the bridge when you come to it. No point worrying now about having no milk, etc. now. It will only make things worse. I think the most important thing is that you've decided to breastfeed your baby. Just eat well, stay healthy and get plenty of rest.