I had the same failure many moons ago and the Cummins shop did not carry the TPS. They say it is a "Application Specific Part" as in Dodge, who makes you buy the whole friggin assembly. The claim it is magically "calibrated" and must be purchased as a unit.
I got lucky because it was covered under warranty a long time ago and the dealer replaced it at no charge to me.
However, I took a close look at the assembly, and the sensor that is buried in it, it looks just like the TPS that I just replaced in my wife's Grand Cherokee, but I think the connector is different. I'm sure with a little checking, you could find just the sensor somewhere for a fraction of the cost.