Try:
www.pyramydair.com There's plenty of information and costs here.
Ox
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...and a little information on their advantages...
"Precision round balls, copper coated. The super thin coating provides
a barrier between your skin and the lead beneath the copper coating.
Upon hitting the hard target lead stays more confined within the copper
jacket.
Copper coated lead balls leave the barrel and your hands cleaner and
free of microscopic lead particles."