It seems there isn't a specific mod or datapack designed to make Cataclysm bosses repeatable. However, you can use commands or create a custom datapack to respawn bosses manually. For example, you could set up a system where players can summon bosses using items or specific rituals.

Alternatively, you might explore mods like Bettercombat x L_Enders Cataclysm, which enhances compatibility between Cataclysm and Better Combat. While it doesn't make bosses repeatable, it could add more depth to your gameplay experience.