If you need older or hard-to-find scores that aren't on the official portal, community archives often host them: Scribd - Casio Song Books
He uploaded it to a free sheet music archive under a fake name. Within a week, it had been downloaded 12 times. Within a month, a teenager in Brazil had arranged it for choir. Within a year, a pianist played it at Carnegie Hall on a concert grand—but she insisted the program note read: “Originally written for Casio SK-1, restored from a broken PDF in a dusty music library.”