Bicycle Mechanics - Replacement headlight bulb?

I have a vintage teardrop shaped chrome stem mounted headlight. It uses 2 "D" cell batteries and has a screw in bulb. I have tried to locate an upgrade for the standard incandescent bulb to no avail. Called specialty websites etc.

My question is, are there any adapters that can be screwed into the bulb socket to accept a halogen or other upgrade bulb? The light reflector is designed for a round globe type screw in bulb, so any type of pre focused bulb probably won't work. This is a tough one. Thanks

What are the volts/amps/watts on your current bulb? Once you know that then check this website out - http://www.reflectalite.com/ They have upgrade halogen bulbs.

I found bulbs for my 68 Sturmey archer dynohub & taillight there.

They are in England, but shipping is very reasonable to the U.S.

I'm not sure what you're asking here. To replace it, look at the old bulb under a magnifying glass. It should have some numbers stenciled on the glass. There are replacements for just about any bulb ever made, you just have to be able to tell which one you're replacing. Older flashlights had screw-in bulbs. Two D-cells means a 3V bulb.

If you mean you want something brighter, the limiting factor is the batteries. You could get a modern light (and modern batteries) that uses an MR11 halogen lamp and cobble up some way to mount the lamp inside your headlight.

I want to upgrade the original 2.5v round screw in bulb to a halogen/krypton bulb without doing surgery on the light. This is a vintage lamp that I do not want to replace with a modern Cateye etc.

No way, afaik.