1. IMSLP: The International Music Score Library Project (IMSLP) is a free online library of public domain sheet music. You can search for the Professor Theme by its composer, Ludwig van Beethoven, or by its title, "Sonata No. 1 in F minor, Op. 2, No. 1: Allegro."
2. Musicnotes: Musicnotes is a commercial sheet music website that offers a wide variety of arrangements for the Professor Theme. You can search for the theme by its title or by its composer.
3. Hal Leonard: Hal Leonard is a major music publisher that offers a variety of sheet music arrangements for the Professor Theme. You can search for the theme by its title or by its composer.
4. Alfred Music: Alfred Music is another major music publisher that offers a variety of sheet music arrangements for the Professor Theme. You can search for the theme by its title or by its composer.
5. Sheet Music Direct: Sheet Music Direct is a commercial sheet music website that offers a wide variety of arrangements for the Professor Theme. You can search for the theme by its title or by its composer.
These are just a few of the many sources where you can find sheet music for the Professor Theme on the piano.