This is a Dyson vacuum cleaner style post-motor filter assembly for the upright DC24. It's in a bright purple with a red tab, and fits in the ball assembly at the front. Once it's clogged, it will keep blowing the filter out and becoming noisy.
As it's light, maximise the saving on postage and buy several of them, or some of the related parts below.
At the moment, standard postage within Australia is capped at a maximum of $20!