Hi,
If you havenīt already solved your problem this may help. I also changed my chainplates from stainless, but to nickel aluminium bronze. Supplier is a UK company whose main customers are the aerospace industry (
http://www.cnalloys.co.uk/). I didnīt think to check the source of the raw material. Finding the appropriate bolts was a problem, as the existing holes in the bulkheads are metric, but that has now been solved too.
Regards,
Bill Attwood