Put in a card that says you offer a substantial reward if the wallet is returned. That might work better than a baby.
Or a note attached to one of the bills that says: There’s a lot more where this came from.
The finder will misinterpret that true statement, and think there’s a reward. In point of fact, there IS a lot more where that came from . . . the Bureau of Printing and Engraving in Washington, D. C.