Hi Tim, this company makes and sells the magnetic plugs you are looking for:
http://www.mintor.com/EN/index.html. Some time ago I bought a few from them and they were absolutely OK. I have not seen any difference between copper or fiber washers as long as they have the correct diameter. BTW, when fitting new points to the distributor, it is very useful to set them with a dwell angle meter (57 +/- 3 degrees) and it is important to check the ignition timing that is bound to be altered. Andrea