NilfiskCFM industrial vacuum cleaner 400mm x 50mm wheeled floor nozzle (WFN) with rubber lips. The clearance height of the lips can be adjusted by the knob on the top. Usually used with the NilfiskCFM127 and the NilfiskCFM137 and the NilfiskCFM S2 and the NilfiskCFM S3 and maybe the NilfiskCFM T22
It's similar to the one in the photo, but that's a 70mm diameter nozzle, for illustration.
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 dustbags, the filters or another accessory!