Mirror top track replacement and hardware

I currently purchased a house with a mirrored bypass door where the top track is shorter than the opening. I would like to put a longer track on the top in order for the door not to come off the track. The current track is a double "J" track and the outside wheel diameter of my current top roller is a double wheel with a 7/8' outside diameter. I am looking for a 60' track I can cut to a FULL 48" width or a track that is a FULL 48" to begin with. Do you still have this type of track, as I did not see such an item on line. But if this is no longer available, could you tell me what single wheel roller would work to replace my double wheel roller which might work so the door does not come off the track. The third option would be to tell me what is currently available to allow to allow me to keep my doors and put up new hardward in order for them to bypass each other.