Are you talking about an extended warranty? If extended I got mine from Granger online but there are a few others that folks recommend especially on the F150 forums.
It’s definitely at the top. It appears to go away if I crack the back passenger window which seems odd. But it doesn’t rattle all the time which is making it hard to locate.
I just got a 25 Badlands non SAS and it was my understanding all 5 wheels had the sensors but not sure how to confirm. I just looked in the Fordpass App and I only see psi for the four on the vehicle.