I have a work colleague who restores old scientific instruments, cameras etc who was looking for obscure replacement 6v 5w BA9s fitment bulbs. I sent him a URL that might be useful.

I received this url in reply:
http://www.donsbulbs.com/ with a note advising me that I should also have known that a filament type C6 was required!

Likely manufacturers being Osram, Orbitec and Candlepower Inc.
Sometimes members of this loose circle maybe recognised as 'oddball' or 'nerdish', but this raises the bar in my estimation.

May I suggest the url is placed on the Recommended Suppliers forum, with a caveat, until somebody has used the service? You never know when you might need that bulb!

I'm off to be a sunbeam!

Bill.