Replacement parts for Stanley/Monarch 60 x 78 mirrored bypass doors.

I am searching for 2 separate parts for a Stanley/Monarch mirrored sliding bypass door physically measuring 30" x 78", (X2), at the frame's exterior. (I imagine this would be considered a "60 x 80" combination, but I yield to your expertise in this area.)

1) Am looking for 2 of the top track roller assemblies to replace on one of my doors where the rubber wheels have deteriorated and fallen off. (Photo #1 shows those that are still intact.)
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2) I need the plastic piece which fits in the center underside portion of the bottom channel to which the metal channel is then secured to. (It would almost appear that one could also substitute an appropriately sized piece of treated/coated hardwood instead, but I would like your opinion on this. It is being mounted over a carpeted floor.