The WAP and Nilfisk-ALTO SQ450 and SQ550 and the Nilfisk-ALTO WAP SQ650 Wet and Dry industrial vacuum cleaner series industrial wet and dry vacuum cleaner rotary cam switch.
It's probably similar to the switch at 3.00 o'clock, but with an open cam mechanism similar to the red switch on the PCB at the back of the photo.
SAFETY WARNING! All electrical parts should ONLY be fitted by an electrically COMPETENT person.
At the moment, 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 the filters, or dustbags and a new floor tool, or other accessory.