I found plenty of them when walking around various wreckers. Just look under Datsuns that would have had these nuts, like 200B SX or Aspen models, plus series one Bluebird LX models as well as any TRX.

People pull the mag wheels & dump the nuts in the dirt, bloody untidy bastards.
I wonder how many came back later to discover the nuts gone. The price is always right too.

I bought a full set of new ones for my 200B SX wheels a while back & I think they cost me about $100 or so at the time.

No, I don't have any spares available as I also have these wheels on my trailer & still have enough wheels left over to make another set.