Nilfisk-ALTO Taski Hako and WAP TW300S dirty solution recovery tank clear (smokey brown) domed lid.
It's the part in the main photo. The other photos are to illustrate how it fits.
This machine has been sold and marketed under many different guises and colours by different manufacturers.
It does, however, have a long history being known as the Hako Homeclean in light lilac colour with a lilac tinted dome.
Taski used to call it the Aquamat 10; it came in orange and included a smoky-brown dome.
The WAP model was yellow and the Nilfisk-ALTO was blue. Each usually came with a smoky-brown dome.
At the moment, as standard postage within Australia, is capped at a maximum of $20, maximise the saving on postage and buy some of the related parts below, such as some hose and other carpet or upholstery cleaning accessory or a Nilfisk vacuum cleaner replacement filters and dustbags, or a new floor tool!