I can make you one of those easily enough - though I would machine it all without taking out of the chuck and turning round as that introduces runout. Make the nylon part first, oversize, then the steel ... push the nylon bit on then skim that and the rest to get it all concentric.

It would be better to have the end a larger diameter than the rest as otherwise any burrs on the part you're probing will touch first, making it less accurate.