greg bender
http://www.thisoldtractor.com/gtbender
Only the Eldorado spare parts catalogs list these light bulbs as MG# 10744910: 12 volt, 3 watt light bulbs. But the specifications end there. You also need a light bulb that has a miniature bayonet base. Here are some part numbers and sources that should work for you. I prefer the #1891 to the #53 because it is about twice as bright (and closer to the original wattage specification).

Bulb style 53 - 1000 hour life rating

Bulb style 1891 - 500 hour life rating