I don't think I've ever seen one either, but I THINK (emphasis on word THINK) that it shouldn't be too hard to design if you can find small enough patterns of the characters.
If you can find small enough patterns, I might be able to help. I can't guarantee them "peeking" around letters though, or anything like that (I'm not an artist).
PM me. And everyone else, if I manage to think of something, I will be more than happy to share.
Donna