Pour it yourself? I am in the UK, and it is available from most steel stockholders. Not cheap, but completely at the other end of the quality scale to window weights. There are some good window weights, can you go to a local scrapyard and go through a pile till you find some decent ones, good indication is to break one in half and look at the grain and colour. Try a file too. Chilled cast iron is as hard as the hobbes of hell, and was used for the rolling mill rollers in steelworks, and low quality window weights will have slag and crap inclusions in them, because they didnt bother to hold the slag back when making them. You could make a cupola furnace and have molten cast iron in 30-40 minutes, after the time it takes to build the furnace!