Valve stem extension for TPMS

I have had to add air to my front tires every 2 weeks on my 2008 Sienna. Finally took it to my trusted tire guy and he said the valve stem extensions leak. When I buy a pack of 4 I only keep the best 2. He also said that the universal plastic extension does not have the same thread as the tire pressure monitor system (TPMS) valve stem. Toyota does not make an extension specifically for their TPMS. I don't want metal as they can seize.



With the wheel covers on it is almost impossible to add air. I have used valve extensions for years on non TPMS tires w/ no problems. The only solution I can find so far is to run w/o wheel covers.