Where can I get guitar or piano sheet music for So long and thanks for all the fish?

You can find guitar and piano sheet music for "So Long, and Thanks for All the Fish" from various online music retailers like Musicnotes or Sheet Music Plus. Additionally, websites like Ultimate Guitar and MuseScore often have user-uploaded arrangements that you can download for free or purchase. Local music stores may also carry sheet music for popular songs, so it’s worth checking there as well.