Pennsyforever,
I believe the Pennsy cars came in the same time the engines showed up around Oct 2020. I got the Northern Central ones the same time I received my York #17 4-4-0. I'm also aware of some folks that bought the UP & CP that they got the passenger cars at the same time.
You might have missed them, could be tough find. BTO items which only work with the special run of 4-4-0.
Best of luck in your hunt.
Jim