You don't have a single head shop in Melbourne? There's always the internet, just make sure to purchase from somewhere reputable. You would not believe the horrors I went through purchasing online because I didn't do my research... If you're going to take the internet route, it all depends now on what you're looking for and how much you're willing to spend. I and I'm sure many of other members of the GC community would love to direct you to some sites that suit your needs. Best of luck finding a bong for yourself!
theres a shitload of headshops around, youll find one every few streets, theres like 10 in and around melbourne cbd, they bongs on display, just walk into one of those stores, ask to buy a waterpipe, cheapest ones are like $15? its suppose to be for tobacco but everyone knows thats not what youre gonna use it for, its perfectly legal to buy in melbourne.