Synthetic magnetic clasp, covered with a metal-plating.
This clasp is suitable for a shoelace of 20 mm width and 2 mm thick maximum.
You can also put many thiner shoelaces.
Glue it with: Hasulith 

To prevent any possible kind of hazard caused by magnet radiation people with heart pace-makers (or similar) should contact their doctor before using magnetic clasps. Price per piece.