To make your own:
Construction layers of the puck ( it looks like a hamburger sandwich from the side)
plastic top with beveled edge
disk of lead
plastic bottom with beveled edge

Hold the top and bottom plastic disks to the lead with 3 screws each side, use flat head screws
that are recessed into the plastic. It is best to screw the screws into 3 threaded standoffs that
are molded into the lead.

An additional step is to then make the lead disk of a smaller diameter that the plastic disks and
then place a ribbon of rubber over the lead. Use neoprene cement to bond the rubber to its self.
You can get neoprene cement from a dive store that sells scuba diver wetsuit cement.

As the plastic disks wear down they can be replaced.