It is available on amazon right now:
https://www.amazon.com/Fantasy-Flight-Games-Arkham-Horror/dp/B07MZCWJMP/ref=sr_1_1?crid=1IK6XNURZPLGB&dchild=1&keywords=the+circle+undone+arkham+horror+lcg&qid=1598610902&sprefix=circle+of+undo%2Caps%2C147&sr=8-1