My friend with the 2007 997 found a mechanic that sold him 4 generic 433 MHz sensors at $55 each. The mechanic charged $100 to program and install all 4 sensors for a total cost of $320. This compares with $195 per sensor that Porsche wanted. Not sure what the installation cost was going to be. After 10 minutes of driving, it was showing the readings for all 4 tires on the TPMS screen. Success.

If anyone in southern Ontario needs to replace their TPMS sensors, my friend or I can provide you contact information.