It seems that these books are only available through other sellers, *not* Amazon (out of print?), and they determine themselves if they wish to ship internationally. There are a couple of sellers who state they'll ship internationally (New or Used) - if Tassie and/or Australia aren't coming up, you could drop them a line and ask why.
I've had success asking about certain books, even when they haven't listed international shipping, so you haven't got anything to lose.