http://www.proto87.com/model-railroad-motor-upgrade.html
http://webspace.webring.com/people/ib/budb3/arts/motor/pit71nmag.html
here’s a link to the micromark page: http://www.micromark.com/super-magnets-20-pieces,9966.html
and here’s an old thread: http://cs.trains.com/mrr/f/88/t/120264.aspx
good luck