Try looking at this and measure to get the right shape and size then find the one with the insert you are looking for.
http://tacomarine.com/cat--Rub-Rail-...rail_kits.html
They are the ones I have used in the past when no old rub rail was available to match. ALways looks good. Just do it in the hot sun or have a big pot of warm water to help it take the shape you need.
There may be others out there but this is what I have used. Web site is good and you can order them from West Marine to get it closer to you and save on shipping.