Going to Sydney for a week in March, was wondering if there are any recommended gadgets I should get while over there if they are cheaper?

Any recommendations on SIM card/plan for mainly data for the few days that I am over there to use with an iPhone 4S?

Also, any recommendations on the best/cheapest place to purchase a new mobile phone with a decent camera around NZ$300-NZ$400 while over there?

Cheers guys : )