Recently stumbled across this web site - www.GlowUniverse.com
that has a novelty item that is a painted eyeball with LEDs installed inside and is designed to be worn on different fingers on your hand. These rings are offered at just over $1 each with shipping. If you use a razor blade and carefully slice open the silicone mold you will have yourself an eyeball to install into your project.
Future project using a pair of these eyeballs.