Here are large parts of the 1st act, composed by Johann Mederitsch (alias Gallus) publicly downloadable: https://digibib.mozarteum.at/ismretrorism/content/titleinfo/2296663

However, the overture and the section from the Priest’s March to the final chorus are missing.

Therefore, the editor had to orchestrate these sections himself, as the piano score is available for free download from several sources.