Cannot find where to purchase differential sensor

I was referring to the sensor that's located on the differential not a wheel sensor. I have looked everywhere also and the Lincoln dealers tell me the same thing, they don't make them anymore but was hoping there might be a aftermarket or a cross reference to another Ford part such as Mustangs IRS but maybe out of luck. Again it's the sensor located on the differential not a wheel sensor, maybe you can provide a name or part number for that sensor. Thanks for your help.
Peter Gray

Thanks buddy, I finally found one here in San Diego, thanks for your help. I thought there were sensors on all 4 wheels in fact I found parts that said they were for the rear wheel and included a backing plate, haha. The older I get the less I know. Thanks again. Now how do I replace the pan gasket, someone told me I have to pull the engine for that chore.