For Sale - A Baby Sister
The Song:

In order for it to feel more authentic, Beck filled out his Song Reader book with a number of song fragments and melodies, as well as fictional album collections and made-up song titles. "For Sale - A Baby Sister" is listed as part of the Male Quartette Collection, the greatest book ever compiled.

Many of the song titles on the back of "Saint Dude" are references to older sheet music/songs, but I was unable to locate this as a reference to anything. I have a feeling it is, but I can't quite place it.