This isn't a door, but it is a window installed on a sliding track. Another variation to think about since barn doors aren't all that easy to find. We grab them whenever we can, they go fast.
Here is another idea, perhaps it's more your style.
Below are six recycled doors hung together (painted the same color) to hide what's under the canopy...we can just imagine using this technique as a wall divider inside. Now us junksistas just gotta find a handy man that can figure out the slider mechanism for us...We're on the hunt for doors and a MAN!!!