thats why you sneak in a Casio Scientific Calculator
, there was no way I was using that tiny piece of crap they gave me, after doing the hsc only 2 years ago, I am somewhat attached to my calculator!!!
Pocket it and bust it out when the examiner sits down, even if they notice it, most don't bother interrupting you if you look busy/stressed. I used it for all exams
But if a Calculator transition is no biggie, you can buy the exact Calculator given to you in the exam from:
http://www.aft.com.au