I am looking for stuff with high antimony content...pewter fits the bill.
A typical European casting alloy contains 94% tin, 1% copper, and 5% antimony. A European pewter sheet would contain 92% tin, 2% copper, and 6% antimony.
European pewter can contain as much as 10% antimony.
You might want to do some research on pewter. It's used for it's high tin content. You want a source for antimony, it's not pewter.