Another thought: Maybe they're looking for the 12th volume specifically. The 12th volume is "Morgoth's Ring", correct? It's a bit harder to find, sometimes out of print. So perhaps suggest checking used bookstores or online retailers for affordable used copies. Also, maybe look into university libraries or interlibrary loan services.
Whether you are a scholar, a fan of J.R.R. Tolkien, or simply interested in the history of Middle-earth, this series is an essential resource that provides insights into the creative process of one of the most famous authors of the 20th century. the history of middle earth volumes 112 pdf free