if u dont really wanna fork out cash for a mobile, some network providers will give u a pretty basic outdated fone for nix, so long as u go on contract (on the '3' website they have atleast one $0 fone on contract..)
otherwise if u are already on a contract, Aplui St Sham Shui Po has some cheap, but brand new outdated mobiles (eg $300 area) ... (i know it across the water from u, juz trying to help

)
maybe u shud grab a spare whilst ur there? he he he, sorry, couldn't help it.
also, buy a lanyard (spelling) and keep ur fone hanging from ur neck
