Because of this, sheet music is fairly common and I see it at estate sales frequently. It's not worth a lot, but I still pick it up if I like the subject or cover. Here are some Christmas related music sheets I bought at the church tag sale a while back.
Per reader request, the interior music an lyrics to "I Saw Mommy Do The Mambo (With You Know Who)".
This was performed by Jimmy Boyd, the same singer who performed "I Saw Mommy Kissing Santa Claus", so this is a sequel to that song.