Having been to HK 14 odd times, I recommend you get on the web and order one before you go there. [There are several caches there already]
"The warranty is only valid within the confines of the store !"--many times true.
I live in Japan and have bought my GPS III+, eTREX and eTREX Legend on the web: best price, new gear, works great.
All the best/ Jens