Helmets are typically a pain in the ass since it is a giant compound curve, but this one looks like it only bends around 1 axis. So it should be relatively simple.
You can cut out the standard silhouette out of plastic then heat shape it to the size of your head+wig. I recommend expanded PVC foam (Sintra plastic) for its durability and ease of use.
The visor should be easy, just needs equipment. You can use clear acrylic, but getting it to be that nice compound curved shape will require a vac form. You'll need to construct a vac table, or use the one at a plastics store, then make the vac buck. I've detailed how to do all this here ( http://junkerscosplay.blogspot.com/2...sdcc-2012.html
If you don't want to you could always either get clear acrylic, and bend it to your needs or even use a motorcycle visor or safety helmet visor.
There's always more than 1 way to go about this stuff. Best of luck to you!
Here is my article on basic plastic armor for the helmet.
The headphones were vacformed and they have a lot of complex round curves.