[NJARC] What # 2.5 vac pilot lamp?

[sgt88 at atlanticbb.net]

My 1920's SW converter needs a 2.5 vac pilot lamp.

My new 6.3 vac lamp base 'works' - dimly - natually...but its screw base 
needs to be forced to fit & light.

The converter screw pilot lamp socket measures 0.33 inches diameter.

The new 6.3 lamp screw measures 0.36 inches.

It seems the 'vintage?' 2.5 vac screw lamp has a smaller diameter.

Question: what 2.5 vac pilot lamp do I need?....and...who might have 
one?..or more as I might need spares for other radio????

Regards,
Steve T.