Bob,
I have made them in the past and I have used those rare earth magnets that are good and strong. I made a purchase of a couple hundred 1/8 in magnets so I put 6 in each of my fridge magnets, I have bigger magnets now so I only use 2. Some folks use that vinyl magnetic tape however I have not found it to be very strong holding things. With the rare earth magnets you can drill a hole for the magnet to be glued into. I got my magnets from Ebay.
DW