Where can i get my hands on these books?
The problem is they are out of print. Get your teacher to check their staffroom to see if someone has a copy lying around - unfortunately, Maths staffrooms aren't as full of actual Maths teachers as once upon a time and so quality resources like these are becoming rarer and rarer. The graphs book is a bit fatter than the other ones in that series (the author was head maths teacher at Ascham I believe back in the day) and is light green in colour. The blue conics book is also a quality resource.
As for "harder 3U topics", this 4U topic is the hardest because the syllabus is basically giving the examiner carte blanche to introduce a whole heap of interesting applications from higher mathematical study. Bill Pender (chief author of the 2U/3U Cambridge books and former head of the Sydney Grammar maths department and general Godfather of HSC mathematics) produced the following (thanks to Derek Buchanan for highlighting this one on his excellent website where you will find literally hundreds of past trial papers):
members.optusnet.com.au/limkw/SGS_harder3U_2002.zip
While it is starting to show it's age, this is an excellent summary of the Harder 3U areas that have been pushed and prodded by the examiners pre-2002. Someone should eventually get around to updating this to encompass more recent papers but as is, it is still a brilliant treatment.
Best Regards
OldMathsGuy