Home made tail light red lens
 

Red acrylic plexiglas . 12 V led bulb. Add a turn signal light

I have always saved the white and red lenses from the army flashlights. They can be punched down to make perfect copies.

You can also use commercial lenses
 

Hi

I have cut replacements from commercial lenses. When they are used you get the reflective property of modern tail lights though of course it is only 1 inch diameter.

Cheers Phil