Search is over, just when I'd given up all hope of finding that sucker, it was discovered hiding in the pencil drawer of my desk.  Hmmm, drawer must have been slightly open??  At least now I can properly identify a replacement when next needed.  The bulb is 3mm in diameter and I'm guessing it should be capable of running of maximum 14-16V.  Current draw of available replacements runs from 40ma to 100ma.  Any thoughts on current?

Why is it that one can find all the parts listed for my MTD Plymouth 0-6-0, except I can't find any mention of the headlight, which shows in the parts diagram but no where else.  I found out too late the method used to secure the bulb when splitting the case and even though I heard "something" fall, I cannot now find the darn thing and need to locate a replacement.