Purity Casting Alloys LTD
They sell "Lead Free Pewter" (92% Tin, 7% Antimony, 1% Copper).
Their pricing typically includes shipping from Vancouver. They sell by the pound, ship in small (under 1#) bars which can be convenient, and they don't seem to have a minimum order. Their prices have tended to be reasonable on smaller quantities, but since they don't (or did not last I checked) offer volume discounts, they are not competitive on larger amounts where prices are reduced, and shipping is less of an issue.