Wouldn't a single diode been cheaper and easier or were you afraid of
the voltage drop across it?

True enough...never really thought of doing it that way, actually.

The first thing that came to mind was the manual switch..which is the
way I went.

Electronics class was a long time ago... Alot of what I learned was
pushed out of memory when I was studying for my pilots licence - my
brain was full. grin

If the need arises to replace the switch for some reason, then yes, I
would have to say that a Diode would serve the same purpose,
automatically. The light bulb just never came on bright enough this
time. :-)