They are not and never have been out of print.
You can purchase a set of the books from the publisher, The Circle of Atonement. This URL link should take you to the right place in your web browser:
https://coa-store.org/collections/frontpage/products/workbook-companion-2-volume-bundle
Thank you for your interest in my books. It is always encouraging to me to hear from people like you!
Blessings,
Allen Watson
You can find my commentaries on the ACIM Text here:
http://www.allen-watson.com/allens-text-commentaries.html