Details

50cm of .75mm light guide.
Un-sheathed polymer fibre, easy to cut to size, and glue in front of an LED (use a plastic friendly adhesive, such as clearfix), and drill a 0.75mm hole in the location of the lamp/headlight.
Easily cut with modelling knife, performance can be increased by covering with shrink wrap sleeving.

Either use a coloured LED, or paint the entry or exit point of the fibre to colour the lamp.
The visible end of the fibre can be shaped to a round or flat profile to match the prototype.

Min. Bend radius: 10 mm
Numerical aperture: 0.53
Attenuation: 0.18/km
External dia.: 0.75 mm
Number of fibres: 1