(1) Buy magnetic "paper" and run through printer. Avery makes magnetic sheets that are 8 x 11. I bought mine at Walmart. You can probably find online cheaper.
(2) Print on regular paper, laminate and glue a magnet to the back.
HTH
Also, you might want to visit the Cruise Board. They make lots of magnets for the DCL doors.
I'm doing the 'budget friendly' option for my magnets
Printed on either paper or cardstock, used clear Contact paper on the front and back, then glued on very thin magnets. For magnets, I cut up a bunch of the magnetized ads and business cards I had on hand.