If you have one of the cheap TPMS sensor training devices (roughly $10 on Amazon) you can use it to determine which wheel has a bad sensor. Then you can buy a replacement sensor (set of 4 for $25 or genuine Motorcraft 1 for $36) and just have a tire shop swap it. They should charge you the same as a flat repair. All they have to do is break the bead, unscrew the sensor from the back of the valve stem and screw the new one on, then reinflate the tire.