I think there have been a few versions made on the RPF.
IIRC paul did one with a clear hemisphere and a light up LED in the eye (the back was a casting of a shuttles exhaust from the armageddon movie prop).
I think rylo did one as well, and there was one other guy but I can't remember his name right now. I remember a han solo avatar but the names a little blurry. It's been probably 7 years since it was made.
They all looked amazing, but PH's is pretty much screen accurate from the old tapes we had back then. I remember wondering how the hell the eye was supposed to move when it had a giant threaded screw in the back of it :lol
I lost mine in a move, so I need to get to planning a new one anyway. This might be the kick in the pants I have been waiting on to get it done.
I do remember that the lens from a cheap disposable camera (you can get the used ones free at wal mart or any photo place) is about the same size as the corneal bulge on a humans eye if you want to hardware build one.