The keyboard is a little small as it's intended for Japanese users. Personally, I don't have any problems with it, even though I'm a fairly large guy. More recent models of Zaurus (including the two posted pics of) have USB host functionality which allows you to use USB keyboards.
However, this is currently unsupported by Sharp and not everything works without a hitch. A zaurus requires a great deal of tinkering to get it how you want it. After that, it's totally the best PDA you can buy
You are correct that it would be tricky to get ahold of one in Australia. Perhaps there is an Australian company that imports them from Japan and localizes them, similar to
Dynamism
If you just need it for taking notes, many people find the
TRS-80 Model 100 quite handy.