If you are looking for a definitive musical piece or anthem related to the (Polish Riflemen's Association or the Legions), the most iconic "good piece" is the march "Hej, strzelcy wraz" (Hey, Riflemen Together). The Anthem: "Hej, strzelcy wraz"
This song served as the official anthem of the Polish Riflemen's Association and later the Polish Legions. Written in 1861 by Władysław Anczyc, it is a stirring call to arms that emphasizes unity, sacrifice, and the fight for Polish independence. You can find various historical and modern renditions of this march on YouTube .
For a "piece" of a different kind, the Polish Art Center features historical illustrations and prints like "Kosynierzy i strzelcy" that capture the imagery of these soldiers.
Known as the anthem of Józef Piłsudski's Legions (the "March of the First Brigade"), this is arguably the most famous piece of music associated with the movement that grew out of the Strzelcy.
While technically a general infantry song, it is inextricably linked to the Legions and the Strzelcy tradition, often played during patriotic ceremonies.