Hi!
and I heard you shouldn't switch brands before baby is a year old or something like that.
Would check with your paeditrician on this one. Infant (stage one) formulas are all very similar because they have to provide the correct nutrition for a young baby. In fact, our baby's doc gave us three or four samples of formula to try when I was going back to work (baby was about 5 months) to see which one she preferred and he also told us that as long as she didn't have any gastric issues from switching between formulas, it was fine to use more than one (which we did as our 'preferred' brand was often out of stock HK wide). Some babies are more particular about formula's taste and show a strong preference for one brand or another, but most people I know use what is in HK when in HK and when they have gone home for trips use what is available at their home destination. (I should also note that both of the HK market formulas we used were made in Europe).
If your baby needs a special formula because of certain ingredient intolerances or because of a medical condition, that of course, would be different.
A few brands that I recall off the top of my head that you can get in HK are Aptimil, Cow & Gate, Bellamy's, HIPP, Enfamil and SMA (but stock does sometimes run out).
If you want to check out what imported formulas are available in HK, here are a couple web sites that stock formula from Europe/ other places:
http://babycentral.com.hk/
http://www.tinyfootprints.com/index.php
ps. you might not want to stock up too much on one formula just in case your baby doesn't like it. Know plenty of babies that rejected formula based on taste but readily accepted a different brand, although many also take to the first one they are offered - I guess it just depends on the child. We have a friend who had something like 30 tins of Enfamil from the US that she had been stockpiling for months and her boy wouldn't drink it, so it all went to a food bank.