Any kind of market for chunky copper bars for cementation?

If you guys generally just go to a scrapyard or some such I probably can't beat that. I do copper, crass, aluminum sand casting though and if there's some kind of niche I could fill for purpose made copper pieces for cementation, I don't know some kind of big chunky suckers. I do this type of nonsense anyhow and if it can help fund my own nitric acid addiction...?

If there's a thing, I need dimensions and what would you pay for such a thing? I imagine if you comb the scrapyards you can find good chunks of copper. Mayne of you probably just use flattened out copper pipes.

I have a clay graphite crucible and it's only ever been used for brass and copper. There's no iron contamination in any of my product.

Just trying to think of something I can do so I can keep going at this.