Humble Software Bundle: The Maps Bonanza. This is a current fundraiser bundle of fantasy/sci-fi mapping software. £22+ (about $30) gets you the core Campaign Cartographer software for RPG map makers, plus a lot of add-on packs including “The Age of Cthulhu” (not to be confused with the Goodman game of the same name).
I can’t find this “Cthulhu” add-on pack anywhere except for the bundle, and local searches of the Campaign Cartographer site, store and blog all come up empty. I suspect it’s a combo of two of the packs they release inside the Annuals they release each year? One obviously being Cthulhu City (December 2017), which appears to be free if you dig into their blog.