Carve one out of wood or plaster or some similar material, then form the plastic over it. Vacuum formers are good for this. LEDs could be attached, and wires run to a battery pack, to make the eyes glow -- but then you're going to have lights shining in your eyes whenever they're turned on; I recommend you design this with a switch that lets you turn on the lights just when you want the dramatic effect. (And use relatively low-power LEDs, probably in red, to avoid losing more of your night vision than you must.)
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were would I find all this.
Websearch the keywords. None of this is particularly exotic, and some of it can be homebrewed. In fact, I think there are Instructables on the topic of plastic forming; I know there are many on the topic of LEDs.For that matter, there are several specifically on the topic of Batman costumes.