They make steel for 410To my knowledge I don't believe there was every any available in factory ammo. EVER. Went through this many years ago when my daughter started waterfowl hunting with me. Back then the only option for nontoxic for the .410 was bismuth. Good luck in your search.
Scratch that, that box is lead. Sorry!I've got a spare box of 7 1/2 shot I could part with