Scott, I know you're looking for a pillow case; but the pillows that i have found worked for me are from www.snooztime.com. They make them in various sizes, and the fabric used is machine washable, as is the whole pillow. The pillow's shell is a blend of super stretch nylon and spandex; from which you could remove the polystrene beads, and then stuff it at night with whatever you're not wearing.
I use a small camo one in my hammock as it cradles the neck for proper support. It works even better on the ground, where I use the next larger size camo pillow. They come in tubular and flat shapes. I found my friend's niece loved the camo bear as a hiking companion and then was able to use it as a pillow once we camped. Now, for folks with kids along camping this camo teddy bear pillow could be the answer to keeping their kids' happy; and dual use as a pillow.
The fabric is very nice against the skin.