A very similar item to the Ochre Gnawrock, but instead of carrying a marking, it carries down whatever eye color your lion has. It would possibly be able to stack with the gnawrock as well. (unless that's too OP?)

In doing some research, I think the best candidate would be the African Ackee Fruit, which looks like little eyeballs inside a flower. The item description could be something along the lines of "A strange fruit which looks like eyeballs. Eating it would surely make your lion's cubs have the same eye color as the parent!"