"We stock new and used, hardcover and softcover titles. Most of our new titles are publisher’s remainders and overstocks. Our used books are rated by condition and priced accordingly. Most of our used titles are in very good or better condition. Additionally, we are always on the lookout for hard-to-find or out-of-print titles."
If you are using a curriculum that is literature-based, they have a search feature that includes such curricula as Sonlight, Tapestry of Grace, Beautiful Feet, Five In A Row, and much more. They even offer fundraising opportunities for your group by giving 20% of the proceeds during the designated time on the orders placed by members of your group.
I have found this store to be an excellent resource for our literature-based unit study (Learning Adventures) even though they don't have this curriculum as one of their special searches. Their prices are great and they have an excellent selection of "good" books (vs. "twaddle":-). They also have many out-of-print and rare books that I have had difficulty finding elsewhere.
Take some time to check out this website/store and see if they have some of those books you have had a hard time finding elsewhere. And I am sure the prices will be pleasing to you, too!