Urbanlamb made one. I keep a copy on my Google Drive. It uses the traditional shader, but has inputs for bump maps and other goodies as well.
https://drive.google.com/open?id=0B3nsNVGroEz6YTFsY1pldHdwOG8The colors for the map cannot be mixed/blended, so you will have hard edges on the materials. Make sure that there is no color mixing from anti-aliasing or anything, because it will cause artifacts.