Thanks, I don't know Bob Culver yet, how does one contact Bob? Cheers CraigBob Culver is your man
An alternative is to make some from stainless. Stainless is about 70% the density of lead, so they only need to be a bit bigger.
Uranium decays to lead.better than SS?,depleted uranium comes to mind, a real swords into ploughshires activity, any old tanks anywhere?