I've been trying to get one of the Centralia CCS 7016 UP diners for years, and can't even prove to myself they were ever made.
I'd put in a reservation from Brooklyn when they first came out and it was never filled.
Anybody know? https://www.intermountain-railway.com/distrib/ccs/html/ccs7016.htm
My '72 Chief on Amtrak had a UP diner stuck in the consist, and I've never found an acceptable car for it.
And I never see these things on eBay either. I need an NYC, and two versions of SP.
But, you are in luck with a more common car. The Kato smoothside diner is a UP prototype.