My new bathroom is tiny and the best place, IMO, to put the TP is on the side of the washing machine. Took the original, added some 2mm deep indentations and then super glued the magnets into those holes.

Used these magnets - https://www.walmart.com/ip/Go-Create-Large-Extra-Strength-Magnets-4-Magnets-Total/52828672

Any magnet that fits the dimensions below should work though.
1.48" diameter (37.59mm)
0.2" tall (5mm)