Hi, Sharon,
Thanks for posting and for your long-time support for my 7-book Macdonald Hall series.
I don’t have anything to do with sales, but I do know that Scholastic has a branch in Australia. The address I have is P.O. Box 579, Gosford, NSW 2250. The email address is [email protected].
The original publisher is Scholastic Canada. I find their website to be helpful sometimes: [email protected].
And this is the link to a Canadian store called Chapters/Indigo for the box-set of all 7 books. Sorry, but I have no control over the prices:

https://m.indigo.ca/product/books/macdonald-hall-the-complete-set/9781443128193

Please let me know how it goes, Sharon. Happy hunting!
—-Gordon Korman—-