You will need 2" white vinyl blind slats. Browse around a home improvement store in the area where they cut blinds to fit. If you cannot find the free ones to recycle, buy a small box for around $7. This will be enough to make hundreds of magnets. While there, buy the 3/4" ceramic disc magnets. Eight for less than $2 and they are heavy duty.
Use a dedicated pair of big scissors and cut the blinds in 2", 2.5" or 3" pieces, depending on the size of your graphic. You save and use the pieces with cord holes too. Use fine sandpaper or an emery board to smooth out the cut edges and round the corners. Wipe them off with a damp towel.
I do one of two things to prep: Cover the edges and part of the front edge and back with a Krylon metallic leafing pen and seal with Aleene's Paper Glaze. Or paint them completely with an acrylic paint. You may want to leave them white.
If I could draw or sketch I would. But I can't, so I print the graphics, laminate the page (Xyron 900) and trim. I run them though a Xyron 510 for adhesive and BAM!, you've got a magnificent magnet. A glue gun or Beacon's 3-in-1 will work best for the magnet piece.
Your cropadile will easily punch through this material so the possibilities of how to alter are endless. Click below for a few examples I have made.
Enjoy! Examples and Varieties