Well, you could maybe shorten it to Jr? Otherwise, there aren't a lot of choices.
Famous people named Junior:
Singers Junior Marvin and Junior Walker; mixed martial artist Junior dos Santos; football player Tiaina Baul "Junior" Seau, Jr.; NASCAR driver Robert Glenn "Junior" Johnson, Jr.
Your little Junior might want to watch the 2016 animated movie Storks on repeat, seeing as the top delivery stork's name is Junior.