It appears five or six of those pics are the metal end cap to where the rub terminates on the stern. I'm not sure you're gonna find a replacement for it. Best to polish it (or paint it) and let it be unless you have a shop to duplicate but it looks in good shape. The kit comes with end caps that are completely different so they are useless. I may have an unused end cap from one of my spare boats but don't hold me to it.
This is what I recommended...check those specs though against yours though since I didn't see overall height from your pics. I ordered off of eBay from a marina out of Florida. It is 50 feet in total length. Can't remember what I paid for it.
2nd OPTION. They have this in black with chrome which is what I have on my Rider but do not have the number for it. See pic below.
This shows frosty white number which you probably don't want. Just showing you the specs are a bit different than rubrail above.
Hope this helps. I'm going to be out of town the next week so will check back later.