Well, besides the Romance of Reynard cycle (which can be found in different forms around the internet) I'm afraid I can't remember anything specific where I might have come across pre-Grimmified folk tales, beyond "my local library" (seriously, I spent a lot of time in its non-fiction section), and then, I'd come across stuff "here and there", not in one specific book (though I do remember a collection of Coyote tales from North America that explained and did away with the censorship that white scribes had imposed on most Native tales - those are mostly dirty, with the usual amount of storytelling violence.)

Best bet might to be to ask at some literary nerd forums; they'd also know what's available now (the number of books that haven't been digitized is breathtaking.)