Scotchbrite TM, Marca Registrada pads are green scouring pads that are used in the kitchen and wherever else you need a tough ally that's good at scratching crud off of whatever. They have a rather open weave, appear to have flat surfaces and are very rough to the touch.
Generic copycats are available in the US, but they aren't as rough and don't last as long. I'll be surprised if an equivalent isn't available in Australia. Because of their open weave, they don't hinder air being sucked into your box much. I doubt that they trap very small dust particles, but I don't have first hand experience with them.
There's a guy that posts on the BBS at
http://www.overclockers.com.au who's possibly the world's authority on using pantyhose for PC air induction filters. He was a SysAdmin at a girl's school in Oz, having plenty of discarded pantyhose came in handy. If you have a wife or GF, this makes getting pantyhose a bit less embarassing, I should imagine. They don't seem to last long, so the world isn't starved for used pantyhose. I think you're supposed to wash them before you use them.
Another option is using the anti-static tear-away sheets that are used in clothes driers. It's suggested that you use them before taping them in place over an intake fan. And there are filter holders/fan guards as well. Dunno about those.