I believe the doors were built semi-custom -- a modification of an typical door, it should not be too terribly hard to find a manufacturer to do this. It is also possible to get a cabinet/millwork person to build them. Since the are not exterior doors, there are not a lot of complications.

There are a number of manufacturers of sliding "Barn Door" hardware as they seem to be pretty common right now. In this case we have had the millwork sub build a box around the hardware to give a a more clean look.

We felt it was really important not to have a floor track in this installation. There is a slot in the bottom of the door that allows a pin in the floor to keep the slider from swinging.