An apparatus includes a plurality of beads, and a linking assembly. Each bead in the plurality of beads includes at least one magnet and a unibody housing encasing and sealing the at least one magnet. The unibody housing includes a magnetically inert material being formed of a particulate powder composition. The linking assembly joins the beads together such that the beads and the linking assembly in arranged in an annular arrangement sized to form a loop around an anatomical structure of a patient. The loop may transition between a contracted configuration and an expanded configuration while being magnetically biased toward the contracted configuration by a magnetic bias of the beads.