The heater temperature push button on my 1996 S420 is not working. The white plastic button that pushes the temperature increase switch/button is broken. I am wondering where I can get the white plastic push button. I have searched and did not have any luck getting one. I hate to replace the whole unit just to get the get the plastic button. The unit still works by removing the plastic cover and manually pushing the switch/button. I am attaching pictures of the button and the temperature controller unit.