This is the response from EDwinter as of 9/21:
Yes, I've been told that there are still no Winter tires freely available for the M5, so I cannot buy any at this time.
It may change as we get closer to November.
Regards
John
www.edwintertires.com
No additional information available yet from BMW NA, so I guess I'll just have to re-route, but only had a couple of days exposure anyway.