Our underground explorer is certainly going to need a light to see where he's going. Last year at a yard sale I acquired an old physician's head lamp. Nowadays these head lamps have LED's for the light source, but this one has a bulb, and three multi-jointed arms which allow it to crazily point in any direction. Very mad scientist looking. I've decided to mount this lamp on a comb (also called a crest) which is on the top of the helmet.
Today I designed it and cut out the pieces of the comb in ¼" thick plastic, and then glued them all together. Above you can see the individual parts.
And here is the assembled comb bolted to the top of the plastic astronaut's helmet. I will be covering the comb in molded leather, and the lamp will attach to the front vertical surface.