I replaced both the weatherstrip and the run channel on the liftgate just last month:
Part# 68290-35031, WEATHERSTRIP, ASSY (this piece is the outer weatherstrip or "belt" that is horizontal (with the end covers).
Part# 68275-35020, RUN, BACK DOOR DL. (The Run is the entire weatherstriping that surrounds the entire window).
The Weatherstrip Assy or "belt" has the end cap or cover on each end. In fact when I took off the original I could pull each end cap (or cover) off. I almost kept them, but since I just replaced the entire unit, I ended up throwing it away. AFAIK, those end caps or covers cannot be replaced separately - it was part of the 68290-35031 part.
The Run channel does not contain those.
The weatherstrip is easy to remove. Roll down the window and from the inside pop up one end with a screwdriver or something similar. Once started, you are able to pull the entire unit up and off. Replacement is easy too, just position it and push it on until it clicks into place. Just take notice of the wiper stop.
Piece of cake, probably took me five minutes to replace.