I refer you to THIS POST, containing my own funny variation on "Rock-a-bye baby", and a complete original called Lullaby for a Breast-Fed Baby". If I do say so (and I do), this is a lovely little thing, with humor as lagniappe.
If anybody likes that Lullaby and wants the tune, PM me with your email address, and I'll be glad to send you a WAV file as an attachment.