Step 1: Get 1/4 Diameter or 3/8" Diameter Magnetic Spheres
Purchase some gold coated magnet spheres from one of the rare earth magnet stores, one of them I use is Applied Magnets.
Step 2: Measure the Wrist
measure your wrist length, 1/4" or or 3/8" magnet spheres looks very good.
Step 3: Customize the Length of Magnets to Use
connect all the sphere together and tailor the length to fit your wrist.