Brisbane Air Cleaner Sales, will sell over counter, in Brendale area
They do couple different sizes and lengths.
Or try Unifilter, website, they are based in Sydney, will sell direct.
Get the internal spring, as, at full noise the whole sock will suck into carb throat, oh, and you need trumpets to slip these over, use zip ties to secure.
Lots of rally cars use them.
If after 2nd hand, i got four red ones to suit your carbs.