Nilfisk CA340 portable electric floor scrubber and the Advance Micromatic electric floor scrubber clean solution filter screen, which is situated in the clean water tank, on the clear solution tube that descends from the top cover.
The photo is of a SIMILAR (a lot more affordable and plenty in stock!) filter screen SKU 7090546 that is just a bit shorter, and is black plastic not red. It doesn't have the brass disc in the end like this part does.
At the moment, standard postage within Australia is capped at a maximum of $25 so maximise the saving on postage and buy some of the related auto scrubber parts below!