Here is discreet and powerful magnets that you can easily use for sewing. You set it by sewing in invisible between 2 fabrics spice pvc. This allows a single seam in square or round but also protects it when washing: it will not rust and therefore will not stain your fabric. Its size and its thinness makes it almost invisible and its strength makes it super effective for self closing.
Please note, this is a strong magnet which can interfere with other products (pacemaker, swipe card)