I'm in the middle of making one too. For my "head band" I'm going to use a vacuum belt. Mic tips I'm not sure yet, maybe painted glue stick caps with screen in the ends. Or some marker caps look like them. For the vocoder I will make it from a product called milliput. It is a clay that cures hard. It can be bought at hobby lobby. The original "stunt" helmets (which were most of the on ones used in the movies) actually had dark green flat lenses. You can cut up a dark green plastic face shield. Yours looks great!