Presumably your rubbing strake is made of wood and not rubber, rebated to cover the join in the hull.
You need to go to a timber yard or boatyard who can Do repairs to wooden boats. Take a sample of your old rubbing strake and they can produce wood lengths with a matching shape.
This will than have to be bolted on.
Or you could replace it using a B Section rubber with a stainless steel middle. This only needs to be screwed on with stainless steel Self tappers from the outside. This methods eliminates having to take all the linings down inside to locate the bolts and also does not need treating like wood does each year.
You can buy this rubber from various outlets such as Walker Rubber (Norwich). Do some research online.
I did the rubber option on mine and it still looks great 20 years on.
If you are looking to keep the original look with wood, the only way to really cure that is to rip it all off, drill down about 5 mm into each and all of the ( once upon a time) galvanised bolts, fill in with epoxy mastic. Then fit the new rubbing strake ( ideally in 2 “layers”, as the original, to help you to follow the curve), polyurethane glue, and 400 ss self tapping screws.
I wrote a full article on this in the journalAutumn 2006 , and it was republished last year.