8V 50mA I believe, as are most indicator lamps in vintage Pioneers. Not sure about the size as they get branded all over the place nowadays but the ones I use are about 5mm diameter and about 8mm long on insulated leads.
Here in the UK, 50mA seem impossible to find but 40 and 60mA are available from Pioneer's parts distributor Seme, the 40's look as good as the old ones do. Or, you can change it for a 5mm LED if you can do some basic soldering, high intensity yellow or orange LEDs work fine, just make sure you solder a resistor inline to cut the 8V down so the LED can take it, ask at the place where you buy it form if you're unsure.
Hope this helps.
Regards, TiberiuS.