When looking for a power supply or adaptor, be it for your phone your ipod or any other electrical appliance on eBay there are a couple of things you should make sure of first.
1. The power supply is designed for the Australian market and you won't need to buy an expensive converter afterwards
2. The Power Supply meets all Australian design and safety rules.
3. Always feel free to ask the seller for the Australian Safety Approval Number and Australian Compliance Number which will be similar to N17130 and AS/NZS3112
These numbers or at least one of them should be clearly marked on your new power adapter, if not the legal rammifications are huge in the case of a mishap or fire.