Emgee – thanks for the link. It looks like they hold only CZ121, but worth asking them.
DK31k – I'll ask metalsupplies.com what they've got. I'm OK with cutting larger section down, and they are in my neck of the woods, so I could pick the stuff up – my (limited) experience with industrial stockholders is that they're more willing to deal with small quantities if collected. Again, thanks for the find.
The remelting/casting idea had occurred to me too, but I don't have the kit or experience.
Robin.