I just bought shirts and tops with buttons or I guess tops with elastic necklines would do the job. Good thing is you can still wear them after you finish breastfeeding. Mind you I never breastfed in public though.
I just wore my regular clothes, with a sweater, or threw a blanket over myself. I could never find any nursing tops that were not ugly. I have a friend who would buy nursing tanks and just wear them under her shirt so then she didn't show any skin, and she could wear regular shirts that way.
I saw the ones at H&M and they looked great! If you don't see the tag that says "nursing top", then you won't even know it's a nursing shirt. Very reasonably priced too.
If you are ready to spend a little on nursing tops you can go to Linea Negra in Central. They have beautiful tops and other clothes for during and after pregnancy. They have a website so you can get their address online.
I found breastfeeding two children the tops and dresses by label "Boob" absolutely indespensible. Knockoffs and similars did not measure up. However I am not sure where in hong kong you will purchase these. I am sure that you can buy it online....it is a Stockholm patented design.
Best of Luck m