The head rest is a custom piece both in the films, and in real life. (The sewing on the actual piece is far too sloppy to be a found item.)
If you'd like, these are the schematics I fashioned to make mine, as well as a photo of the finished product. You're free to use them as you see fit.
As noted, the "shell" of it is made of two end-caps with a large piece of fabric between them. On the seams, sew on a strip of black fabric or ribbon as a border.
When finished, shape the padding by cutting sheet foam in your ideal shape of the pad to fill out the pillow how you'd like.
When done, it should look a little something like this: