AbeBooks, both of them priced at over $1,000. Fortunately, the folks upstairs agreed with me. The book, written by Albert Deane, is titled Spelling Bees: The Oldest and the Newest Rage, and was published in 1937. It's peppered with small pen and ink drawings by Dr. Seuss, including a couple of "Horton," as my coworker delightedly noted, "disguised as a bee." This typo is one of "highest probability," according to the Ballard list, and should be looked for and corrected STAT. We discovered 143 cases of Illustat* in OhioLINK today, and "too many records found for your search" in WorldCat.
(Cousin Reginald Spells Peloponnesus, by Norman Rockwell, 1918, courtesy of Wikimedia Commons.)