Do you mean the worklight? The tail lamp bulbs are an odd ball, only the dealers have them. the signal bulbs are easy to find. Haven't got into the worklight yet.
It's a utility light ,4″X5″ , sits, facing back, on the right rear top of the fender. It's controlled by a rocker switch on my panel. I took the bulb to NAPA and the standard replacement is an 1156. Let there be light! BG