No ereader has ever used an HDD or floppy. The Sony Data Discman did have a magnet in the CD rom reader.
https://en.wikipedia.org/wiki/Data_Discman
There is no measurable external field from a modern HDD, floppy, CD, DVD or BD Drive. Any loudspeaker has a much stronger field as anyone that ever sat an unshielded one beside a TV colour CRT or computer monitor Colour CRT can tell you.