I also unfortunately only have the 15 second midi of STEP you.
However, as a pianist myself, a good method I've used for sheet music is to go to Divine Ayu's
midi section, download the midi of the song you want, and then open it in
Noteworthy Composer. The program will display the midi as sheet music, and you can print it out.
Alternatively, LeButler has hosted some sheet music scans which you can find
here.