Nilfisk AX400 and the Nilfisk AX300 and the Advance Aquaclean stainless steel mesh clean solution water screen. It fits in the clean water tank as a push fit into the water outlet in the bottom of the clean solution tank, that's the second photograph.
I've taken a photo of a screen from a working machine, don't worry, you'll get a brand new one!
If the cleaning solution is left in the tank for a few days, the chemical mixture can break down, and it can form a gel blocking this screen so the water or solution can't flow. This filter then needs to be washed off.
At the moment, as postage is capped at a maximum of $20, Maximise the saving on postage and buy several Puregiene toilet rolls a box of Tissues and some soap or maybe some packets of dustbags, or a hose or a new floor tool, or some other accessories!