I wonder if you could glue two of them together and then trim the seam and sand to get a full round eye.  I have a feeling these are more rigid then ping pong balls and would hold up better which is why I am asking.

they sure are and don't see a problem at all gluing them together. to glue styrene an make it really hold you need to use a glue called "Zap" it's a little tough to find out in the stores but works perfect

Shawn if you'll look on my Designs of Hollywood website I offer Pro Costumes and props of all sorts. I bet We could help one another. your puppets are really something else

Wow! Thanks for explaining that.  I might give it a try (in my spare time haha!).