Nilfisk GU350A and GU450A Microstatic Exhaust Filter Pack of 5
These are the white filters that fit under the grey grill at the front of the upright part of the machine. I suggest a fresh one is placed in there after each pack of 10 dustbags has been used.
At the moment standard postage within Australia is capped at a maximum of $20! So maximise the saving on postage and buy some of the related parts below!