Anti-Aging for Mobs

With the new baby mob variants coming out, some would like to keep them small forever, so maybe some type of item to stop them from growing past the cute and huggable baby forms would be great. Maybe if you craft a nametag with all ore nuggets or with amethyst which it would make a different type of name tag which works the exact same, but freezes aging.  It could also be found naturally in mineshafts and dungeons, though rarely. And sometimes a master Villager with the librarian profession would sell them for 30 Emeralds.