What do you mean by power adapter?
The rating sticker on the power supply should tell you if the adapter is a universal type, ie 100VAC - 240VAC, in which case all you would need would be a physical plug adapter. Otherwise, if the rating sticker specifies a fixed voltage, then you would need a 240V-110V transformer. Since such transformers are expensive, it would be cheaper to purchase an Australian adapter rated at 12V, 2A, centre pin positive.
