Genuine Nilfisk GD5 Commercial backpack vacuum cleaner packet of 5 white paper dustbags with adhesive seal. Will also suit the GD10.
They actually seal better if the adhesive seal is exposed by removing the white cover paper.
This machine is also called The Adgility 6XP. The Back Vac 6 and The Comfort Pak 6.
It comes complete with the white round pre-filter for the motor.
As they're light, maximise the saving on postage and buy some of the related parts below, such as the filterbags and the filters or a new floor tool.
At the moment, standard postage within Australia is capped at a maximum of $20!