Not sure exactly what you need. Are there any markings on the bulb? Sounds like this maybe?
Its not an old bulb, just a British bulb. I believe there are a few sites state-side that sell British bulbs, but you may need to order from the UK and ship it over (search the threads). You need a Bayonet mount bulb.
This look like the bulb? http://www.ebay.co.uk/itm/10-x-Light-Bulbs-BC-B22-Bayonet-Push-In-C...
Forgot to ask, are you running the lamp through an up-convertor?
You need the type in this link,
I bought an old Crestworth Mark 1 Astro lamp that had that style bulb. It was fairly easy for me to rewire it using an intermediate socket wired to a salt lamp dimmer cord. I know it isn't keeping things original, but the wiring was old anyway and once something gets to be that old, I think it is just safer to rewire anyway. If you choose that route I would be happy to post details. I actually bought 3 different sockets to see which would work the best. The candelabra wasn't good for the Mark 1 since it was somewhat defective (the socket thread was not done well so it made the socket come at an angle... but it was the right length socket... not all candelabra sockets are the right length). I also bought some halogen sockets but decided it would be easier to use the intermediate in this case. The Mark 1 is a bit of an different design so it had some space limitations.