Q. I am trying to locate Simethis seeds or plants.
As you probably know this is a rare endangered plant from Ireland and the UK. We have not been able to find any source for this species. One suggestion is that you contact various seed exchange societies and see if they will put it on their "want list" e.g. US Rock Garden Society - https://nargs.org. The Scottish Rock Society used to have it listed but it doesn't appear on their latest list. - .http://www.srgc.net/index.php/extensions/seed-exchange.