Most of the better power supplies come with a 120 - 240 V switch... You might need to replace the power cord if obtained from US or Japan. And most of the better power supplies are quite capable of handling 50 or 60HZ frequencies. (switching power supplies really don't care about input frequency, as it is all converted to DC anyway.)
Another issue is most of the overseas e-tailers won't ship overseas. So in AUS newegg, tigerdirect, et al are out.
A good source for local parts is staticice.com.au....