(Quote edited.)
"Using something heavier" than lead made me curious. Google told me this: "...gold with a density of 19.32 would be a possibility. Other relatively available elements that are denser than lead and without toxicity concerns include palladium (12.02), rhodium (12.41), tungsten (19.35) and platinum (21.45)"
https://chemistry.stackexchange.com/questions/13908/something-denser-than-lead-but-with-lead-like-properties#:~:text=Other relatively available elements that,) or silver (10.5).
I think those numbers are for specific gravity, which is a concept I dimly remember from high school. It compares the weight of a given volume of a material to the weight of the same volume of water. (I hope. I'd hate to disappoint Mr. Ihlenfeldt.) The specific gravity of lead is 11.34, anyway, which seems to fit.
I think uranium is heavier than lead too, but that's probably where that bit about "toxicity concerns" comes in. I would go with gold or platinum, just for the prestige. I mean, who's ever heard of rhodium?