Source of rolling doors

I want to replace some of the interior bifold doors I have in the house. These are doors to closets, utility rooms etc... but I cannot find anything to my taste in the typical home centers.
I saw in magazines rolling doors for closets. It looks like from the picture may be a horizontal frame (may be some sort of channel) is mounted on the outside above the opening, and may be the sliding door just rest on it with rollers? Not sure if there is anything in the bottom or not. The door can be pushed all the way over which makes the access a lot better than the standard bifold doors, and does not involve the expense of ripping apart walls to install pocket doors.
Is there a source for these doors? Are these custom made? What parts are needed for the sliding mechanism?

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