What about this?
Nano Spot - Miniature Spotlights - FrightProps.com
LED mini spot, 12v, 0.25w, supposed to be a 30 degree beam, might be able to hide it under the side edge of the helmet, one of each side?
I know that is not very bright. The purpose of the helmet light would be a "signaling" light - to point it at drivers and get their attention, so they don't pull out in front of me, etc. The bike wears a regulation "light up the road" light.