When I ran out of storage space in my pantry I put an old Spontan magnetic board (the vintage version was white) in the ceiling. In order to do so I had to drill a hole in each corner to provide access for the screwdriver and use washers to cover the slotted hole on the backside of the board.
I then salvaged a bunch of hard drives from the local electronics recycling bin and dismantled them to get the neodymium magnets.When you have got the part the magnet sits on (the part is made of fairly soft iron) put it in a vice and use a polygrip plier to bend the surface the magnet sits on. Then use a screwdriver to pry the magnet lose.There is two magnets in each hard drive. Its a little work but free super magnets beats buying expensive ones 🙂 Also be careful handling them, they are REALLY strong.