to be honest, if this is a high priority item, i would just take a slightly longer transit, and take the AEL down to the apple store in ifc (hong kong station).

if you have even more time to spare, first apple store for your macbook, then stop at kowloon station for "io.t by hkt". this is a store operated by the largest mobile carrier in HKG (csl.), and they are selling iPhone X 256GB for HKD9288 without any contracts.
(downside is, buying from a mobile carrier means they make you open the box and activate on the spot as per agreed with Apple)

good luck~