I bought the same as Tommy recommended and it works great. Like he said, the 277 and 276 are the same size. I actually cut a door in my cover where the pup's door is so I could access without pulling up the cover. I reinforced the edges with duct tape on both the new door and the remaining cover....then added some velcro to keep the new door attached to the cover and in place. Don't need it often, but handy when I do.
2014 Rockwood HW277
2014 Grand Cherokee V6 2WD