The book by Terry Lee that was mentioned can be purchased from his website here. These cost is $72, but this doesn't include postage. The school can't obtain it any cheaper. I know that it is expensive, but it is a good resource and you may be able to on-sell it next year.
The book by Graham and Denise Arnold can be purchased locally; the Book Warehouse can order it, or if you prefer to go online, Fishpond have copies.
Otherwise, use as many books as you need to - there is no one book for Extension 2 Maths that does justice to all topics.
