Debussy Étude 9 Pour les notes répétées is the one that immediately comes to mind
There’s this Prokofiev piece. It’s a nice study in 4ths.
I took a look at it, and it didn't seem to have many double notes, but Nos. 2, 3, and 4 from the set for thirds, fourths, and sixths definitely seem to be what I'm looking for!
Czerny is excludedLet me know what else I am missing.
You are probably missing Czerny's "Toccatina" from his Sonata No. 5. Czerny also wrote music.
That's debatable.
If you're saying it's debatable that Czerny also wrote music, I say, no it isn't! And here is my evidence.
I was being facetious and could not resist
Here is nice collection:https://imslp.org/wiki/School_of_Double_Notes_(Philipp%2C_Isidor)