If you're looking into backup/archival copies for modded/hacked Switches (Atmosphere, etc.):
While "NSP" typically refers to the digital game file format, official DLC for this title is usually distributed as free updates or bundled with physical releases: Package Version Bonus : Includes exclusive units like Grandon Mining Corps (Mallet, Driller, Piledriver, etc.), plus 10,000 Cat Food. Serial Codes : Exclusive cats like Manga Boogie Cat have been distributed via codes found in CoroCoro Magazine unlock requirements for any of the new SUPERFEST units or Advent stages? The Battle Cats Unite!/Patch 1.0.8 Update 07-Jan-2026 — The Battle Cats Unite- SWITCH NSP -DLC Update- ...