Bulb is burnt out in factory reciever

I have a 92 mustang LX. It once had the factory ford tape deck receiver. A couple of years ago my brother took it out and put in a Pioneer one. Well he got a new car, put the Pioneer receiver in that, and put the original stereo back in the mustang. It works fine, except that it doesn't light up. It has sound and everything though, if you shine a light on the LCD part you can see the time or the radio station. We put the stereo in a Ford escort and it did the same thing. All the fuses are good. I took the stereo out, took off the back cover, and suprise suprise, there was no bulb in there! (even though my brother "knows nothing about it). So I guess he took it apart and never put the bulb back in and it is lost. I tried putting in an LED and it lit up so I know it has power, but the LED is not bright enough. I need to know what part # the bulb is and where I can buy one. I need to do this soon so I can sell the car. THANKS!