Nilfisk SM800 and the ALTO Floortec 480M Sweeper Side Broom. These are black nylon bristles and 2 are needed on each machine. This is the part number and price for a single brush.
Note: I've used a photo of a better quality side broom, the true side broom is plastic with a single fixing hole. I'll update the photo soon, Andy 24/09/2021
At the moment, standard postage is capped at a maximum of $20 within Australia, so maximise the saving on postage and buy something in the related parts below!