I missed the NC in the prox switch part number so my suggestion for a normally open switch doesn't apply here.
The wiring suggested by TPS could work for PNP type switches, however you have NPN. In the attached drawing the top is the TPS circuit. The bottom is a similar circuit for NPN NO switches. I can't guarantee it will work for your prox switches. Among other details, I don't know how much voltage drop there is to the output.