Tell us where you heard about lead rings in PE, as we may be able to clarify what was intended ?
Some PE-ers use golf weights for hanging. I think some of them are lead. Search on Golf weights in these forums; I think there are diagrams in some threads showing how to wrap and hang with them.
I wouldn’t wear a lead cockring next to my skin, because lead is poisonous. I would also expect it to be too soft to hold its shape.
If you like the fat donut type cockrings, try these:
Stainless Steel Donut Cock and Ball Ring
– Healthy & Active
There is some advocacy among Thunders members for cockrings, as a means of keeping the cock pumped for longer, a bit like clamping, but I think it is more of an adjunct than a PE technique in itself.