Hey man, looking back twelve years, we now have the ability to revel in Sesame Schickele music. I can't remember how we know he scored the close-up films though. I'm assuming the academic library you had access to?
The registration was "Three Riddle Films" (and the three specifically were tire, tomato, and skin). Either one of the databases (ASCAP now just has a generic "Sesame Street Cues" as well as "Tire") or the copyright catalog, plus it also pops up in his 1980 Current Biography and elsewhere.
ASCAP also lists him as doing "Cornfield," which would be this. I don't remember it being there before (I half wonder whether he switched from BMI to ASCAP or something, and also some old ASCAP registrations cited in edit summaries no longer apply, so sometimes stuff shifts for living songwriters).
Oh, it's all also in his 2004 bio-bibliography by Tammy Ravas, but I doubt very much that was my original source (both as I would have cited it even then, and as I also don't think Google Books had the text then, but registration and copyright catalog and the ilk, we just put down at the time).