Unfortunately they don't still print the Success One past paper books for IPT but a few libraries allow you to borrow them.There are also Success One past paper books which come with really good sample answers as well as good practice paper with solutions- not sure if these are still in print though so might need to search.
I found that when doing HSC that there were a lot of papers floating around but not many comprehensive solution sets to show the standard of answer required to do well.