FCA Fleet services emailed me back and told me to call their 800 number. I just did that and you'd think I just asked them for a part number for the wheel on the new Mars rover. They directed me to speak to my local dealership. I am at my dealership and the parts guy was unable to find the steel wheel shown above.
I emailed a different dealership parts desk who deals in FCA law enforcement fleet sales. The rep there said that he is not yet aware of any 2021 Durango Pursuit sales and that the rim is new for the 2021 model. He said the number likely isn't in the system yet since it is so new, but to check back with my local dealer in a month or so.
I don't need steel rims until next fall, so I guess I'll just cool my jets for a while. I will post back here if/when I get a p/n for them.