Update 7-13-2017
OK, I Had trouble getting the Batman mask together, so I decided to strike out on my own. I started by making a head form, which is basically just something the rough size and shape of my head that I could use to make a helmet pattern.
Behold, my Evil Twin Skippy!
With Skippy's help, I made the pattern. I started by wrapping his head in tin foil and duct tape (I heard no objections from him), and drawing the important parts from my reference shots of the helmet in the series to get the face opening correct.
Reference shot
Skippy with drawn pattern:
I cut the pattern off the head and laid it out flat on a cutting board.
I used Inkscape to trace the photo into a pattern, and then sized it up about 10%.
I cut out the parts and taped them together to test the alignment and the fit.
I need to make the helmet taller and wider on the base, as well as fix some alignment issues. If I get this to work the way I want, I will be able to post a pattern that anyone could print out and cut out of EVA Foam (floor mats).