I assume you can read music notes (the tadpoles) since you mentioned it. If so try finding sheet music you like on Musescore (the website) and download them with Librescore (proprietary). Then you can open the .mscz file in Musescore (the program) and transpose it to your harmonica's key.
Alternatively, if you can process notes to your key on the fly in your head, you don't even need to download and transpose the sheet.
The sheet music doesn't need to be for harmonica. Don't care too much about all the instruments you'll see. Look for the melody and improvise base on your skill level.
-fellow tremolo harmonica owner