A talented pony fan who goes by zebrasftw1 on Youtube (check out her channel!) has sent in a whole bunch of sheet music, most of it for alto sax. I'm going to do this in bullets to make it clearer:
-Becoming Popular: two versions, one for alto sax and one for any C instrument.
-Cupcakes for alto sax.
-Theme Song for alto sax.
-Parasprite Polka for alto sax.
-Smile for alto sax.
-Winter Wrap Up for alto sax.
-This Day Aria, a duet for flute and alto sax.
You can listen to the Aria duet in the video, and you can find several other recordings at zebrasftw1's Youtube channel. Many thanks for these great resources!