I wish I could help you, Sweetie, but the only two things I could suggest is used model clay to make a half spherical, that's bigger then your head, let is dry over a day or so. After drying, cover it with worbla( http://www.cosplaysupplies.com/store.php?s=UN4V ), then heat it with either a heat gun or oven. After cooling down, carefully take it off and repeat the steps to make another half. From their I would cut holes on the inside, shot you make the face and you can wear it, then hot glue both pieces together. Finally used paint to color it and a clear coat, after it drys, to make it shiny. Atleast that what I used to make my Baymax's head

The other way have to deal with a large ball, paper mache, paint and clear coat.

I hope that will help you,
Hana~

Dat is a good idea.

Glad you like it.

Oh, I forgot to tell you one thing about the worbla way. When I wear my Baymax cosplay, I need to take off the head ever 10-20 minutes, cause it was extreme hot. So, I suggest putting a computer fan or two in the back of your with some good size holes to have a cross breath.

Donno how to help you find your hat but thanks for the new music!

I didn't watch the video first so when you described the mask i thought you were going for something like https://www.youtube.com/watch?v=hMYhMnRxj-0

basically.

Blow up a beach ball. Cover with paper mache. Shape to preference?

https://www.etsy.com/listing/248406182/

Here's a starting point o-o
I am sorry. I am useless person ;-;