I was thinking of perhaps T 1 3/4 flange base. They're found in a
lot of indicators, though the T 2 "slide base" lamp is another
possibility.
The T 1 bi-pin lamp is another option, I suppose.
CML is the usual source of these. I note that they now offer LED
replacements for some of the miniature panel lamps. At any rate,
here's a catalog:
http://www.cml-it.com/pdf/psg_200607.pdf
Most of the big distributors (Newark, Mouser, etc.) carry these.
Cheers,
Chuck