well, like bubz said, its v.difficult 2 tell u HOW 2 find unique material - after all, thats what makes it unique, not many ppl find it!! i guess, 2 start off with, dont use ones that r on the syllabus as related texts - coz every1 who got lazy and forgot 2 look 4 texts will be usin these. however, its not a bad idea 2 look at the author's of the recommended texts and look them up 2 see if any of their other work fits into ur category. id also try searching through newspaper archives, lookn 4 one off pieces (like articles from the heckler, or other opinion-based sections) - usually there'll be somethin there u can use. if u still cant find anythin go look through university libraries etc. the pieces ull find will be harder 2 understand probably, but no1 else is likely 2 be doin them.
4 in-class tasks, it isnt hard 2 find out what every1 else is doin so u can avoid those texts. 4 the hsc...u can always make one up. no1's ever goin 2 know.