Intake air temperature sensor

My 1989 I6 4.0L with 406K miles needs the thermistor that tells the PCM how rich to run the injectors. Dealers and parts houses tell us that it is no longer available Web searches seem to confirm that.

We found two in a bone yard on later models. One of them is dead, the other works - after a fashion.

Can anyone point to a source for new thermistors?

Here is an option.

http://www.jeepforum.com/forum/f12/87-2-5l-air-charge-sensor-replacement-792984/