Bones of the Yopasi

Hi all. Could use some help; hope this doesn't break any community rules! I have every Arkham Horror book pre-LCG, except Bones of the Yopasi. The rest are (mostly) still available here and there online, so . . . why is it so difficult to track down compared to the rest? And is there any hope of reading it without paying $100 or more on eBay?