The ones from Ruger, or from Brownell's sold as Ruger parts are the correct ones to use. The set sold by Brownell's is brass with a steel screw. The thread for Ruger is 6-48, while I think the brass one from Brownell's is 8-32.
Cary Chapman uses a Ruger correct set that is black, but does not sell them separately.
Too bad all sets are stainless or brass. Look O.K. with stag but stand out like a sore thumb on walnut.