I wonder if that isn't half way possible... you made me think of Flexi discs - low quality 7" plastic discs to played at 45 rpm on a record player that were given away on magazines... and then made me think of the magnetic ink that uses to be used on cheques... and then if it would be possible to print a floppy disc with magnetic ink. Low low data density, obviously, and the drive would require custom firmware to read it. Hmmm. There was that bloke who used a 3D printer to print a record - the song was recognisable even though it sounded underwater.