It is so good to "meet" another like-minded person. I love your schooling and the fun you guys have. It looks like a beautiful life. We are not unschoolers, and yet, I feel I have one foot in that camp. (I am now a follower.) To answer your question, I posted it in the comments of that post, but it came from Interact Simulations, which is a too expensive curriculum for what you get. I think they could be hand made, however.
So nice to meet you too! I don't know if everything we do would be considered unschooling, maybe interest-led is the term for us. I do enjoy alot of Charlotte Mason's teachings. Glad to have found your blog through my friend Melissa (Simple Whimsy). Thanks for following our adventures.