27litre pack of 5 they also are for the 

Safety bags consist of a paper dustbag, inside a plastic liner with a Tie-Rap, taped to the liner.

When the bag is ready to be changed, carefully remove paper bag from spout and pull up the plastic liner around paper dust bag.

Carefully twist the top and secure with Tie-Rap and dispose of with the hazardous waste at an designated hazardous waste disposal site.

As it's light, maximise the saving on postage and buy some of the related parts below, such as the filter or a hose or a new floor tool. 

At the moment standard postage within Australia, is capped at a maximum of $30!