Carlos Ayento doesn't list this iris as being in commerce in his 2010 historic iris availability spreadsheet, and it's listed as "Endangered" on his web site, so it may be difficult to find. Since he's the guru of all things Schreiner, he might be able to point you in the right direction - see the link below for contact info.

Here is a link that might be useful: Brighton Park Iris

I see it was bred by Schreiner's and introduced in 1951.

Copper Medallion

On a very long shot, you might try contacting Schreiner's and see what they say about its availability.

Good luck!

Sue

Here is a link that might be useful: all contact info for Schreiner's Iris