Thank you both, Conrad and tomato!
If this were for a small batch or hobby project, I would bite the bullet and buy some old stock parts. (Although they have become painfully expensive, at $40 and more.) But I am working for a fairly large company with strict processes. We are looking for parts with guaranteed origin and quality, and for a long-term solution.
Finding a modern replacement has been challenging indeed. Yes, we may have to try and roll our own. But that is not easy either - the commercial solutions (both HP's old one, and the more recent ones) use split lenses to iage the source and detector to the same spot and obtain the compact form factor.
Still hoping that someone knows about a current niche product -- thanks!