Retail on the Reader is US$350, you won't really find it much cheaper than that. Also, considering you're in Australia, you'll have to make sure the seller ships internationally (and it'll either cost a lot or take forever to get to you).
I found a few (already complete) where the Reader sold for under $350, so just keep an eye out.
http://cgi.ebay.com/Sony-eReader-PRS...QQcmdZViewItem
http://cgi.ebay.com/BRAND-NEW-Sony-P...QQcmdZViewItem
http://cgi.ebay.com/Sony-Ebook-Reade...QQcmdZViewItem