So far as I know the screw hasn't changed, only difference is blue or stainless. The original part number was XPR-33. Now it's PR-33 for blue, and KPR-33 for stainless. I remember a post somewhere about someone putting a new one in an older Bearcat. A call to Ruger in Newport should give you a definite answer.
The ejector housings themselves have changed materials a couple of times over the years.