Mine is similar to yours, but dealer did not add PTT to the build sheet. I got an older set of 4 from ebay for $25. As long as they are 433mhz, they should work.
Optional (and not available on base sierra)
PTT Trailer Tire Pressure Monitor Sensors, includes set of 4 sensors. Sensor functionality requires (U1D) In-vehicle Trailering App to be ordered with the vehicle and installed by the factory. Sensors will be shipped loose with the truck and will need to be installed on trailer by customer. System is capable of monitoring up to 6 wheels. Additional or replacement sensors are available through GM Accessories
1 - Requires (ZL6) ProGrade Trailering System or (PDQ) Preferred Package.