In message , Fredxx
writes

I've tried google images and got nowhere. This is where a link to a
picture might help.

You're right, of course. eBay US item 223553936563

https://www.ebay.co.uk/itm/Lionel-39...-WITH-DIMPLE-B
ULB-NEW/223553936563?epid=1739264075&hash=item340cda5cb3:g :kXIAAOSw5cNYeo
Ob

Intrigued by Andy's suggestion of drilling an LED bulb. Should I infer
that such a bulb (never used one) is plastic, rather than glass?

--
Graeme