1973 Dodge Charger SE Brougham

Looking for the bulb that illuminates the “Fasten Seat Belt” sign in front of driver , on the dash in front of speedometer.
During restoration, was not replaced and cannot find.
Seat belt buzzer will not turn off when in gear and no one in passenger seat until I connect the passenger seat belt.
From a wiring diagram, I see that the bulb and buzzer are connected (makes sense). I would think that the light bulb must be in place for a correct circuit.
My questions are:
1. Am I correct on the need for the bulb in circuit.
2. What is the bulb part number and where can I obtain?