Hi delmont, and welcome. I suggest you take a look at the below link in our wiki, "Where to Buy eBook Devices", as there's more than just the iLiad available in Australia (although I have to say an iLiad's a very good choice!). If you're in Melb and can visit Mitcham, you can see both versions of iLiad, Cybook, HanLin V3 and iRex DR1000S at DA Direct (PM for my contact details, if you're interested).
I've had the same trouble finding ebooks available for us to buy. You could try
www.macmillandigital.com.au or
www.dymocks.com.au. There's also
www.ebooks.com, which is based in Western Australia, but its a bit time-consuming sorting through their offerings to find ebooks available to us. Many are only available to USA residents, for copyright reasons.
Also see
https://wiki.mobileread.com/wiki/E-book_stores