1999 Ford Explorer Air bag readiness light

I have a 1999 Ford Explorer with 300,000+ miles. It’s a great SUV! My air bag readiness light acts strange as I drive down the road. The vehicle has driver, passenger and side air bags. The readiness light will momentarily illuminates when the ignition is turned on which is normal. Then, during a trip the light will remain on or it will flash or it will stay off and then will flash on again. I have been told I need a new circuit located under the carpet somewhere between the two front seats. I have been told the part doesn't exist anywhere in the Ford dealer system. Would you know the part I need and where I can find one? Do I have to go to a junk dealer to pull one out of a '99 Explorer on the lot? Just as important, are the airbags in the car working if the “readiness” light is on? If the light is off? Thank you for your assistance.