Check out
Pilot Practice Page
USA based website which generates FAA exam questions. Change exam type to 'Fundamentals of Instructing' as the FAA CFI exam is based on the FAA Aviation Instructors Handbook (funny that).
You should have pretty good success if you score OK in these practice exams as the CASA PIRC exam plucks it's questions from the FAA with a few Part 61/141/142 Q's thrown in for good measure.