Nilfisk AX400 and the Nilfisk AX300 and the Advance Aquaclean bi-pass vacuum motor filter fitted under the machine. It filters the cooling air drawn into the machine by the fan on the back of the vacuum motor. It can get quite blocked with fluff and no one will realise, until the motor begins to overheat.
At the moment, standard postage is capped at a maximum of $25 within Australia, so maximise the saving on postage and buy something in the related parts below!