Scott ... great tune ... somewhat surprised you had never heard it until now ...

I've looked for the lead sheet in the past with no success, but here are a couple of links for the lyrics and chords ...

http://tabs.ultimate-guitar.com/d/donald_fagen/walk_between_the_raindrops_crd.htm

http://megachords.com/guitar/music/208645/walk-between-the-raindrops.htm

here's a link to the book Bob mentioned:

http://www.musicroom.com/Song/75812/walk-between-the-raindrops/

I would like to know if you come upon the sheet music ...