Parking tube support. It fits under the plug recess.
This usually goes missing after unit has been repaired by unauthorised service people. Supports nozzle and tubes in parked position.
Also used in the and Nilfisk Pelican series of domestic vacuum cleaners.
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!