You know what, maybe just keep this piggy bank for yourself instead of giving it to a kid.
Now that we think about it, why exactly is a piggy bank only for children? We all need a place to keep our change; maybe it's a bowl, or a mason jar, or a hole you dug in the backyard (its location marked by a creepy stick sculpture inspired by True Detective), but regardless, we each have something. Why not use something that subtly reminds us of a traditional piggy bank?