I definitely see you what you're talking about there, Jim. Between the tight radius and, likely, the heat/cold contraction rate of starboard... and since it's screwed tight with no room for movement... it's not surprising that it cracked. I would "guess" that Grady made these pieces in-house, which would mean they wouldn't be available aftermarket... not that you would necessarily want to put the same thing back on there.
That's wider than what I had in my mind and my original thought won't work. The trim piece you linked to is certainly a good thought - I've used that stuff many times. My only concern there would be (1) Aesthetics, since it has a rough looking surface and (2) It looks like (judging only from the picture) the bulkhead, for lack of a better term, may be wider than 1/2".
The trim piece you linked to (or others, I'm sure) often still has a tendency to pull away from tight inside radii. However, an adhesive like BoatLife LifeCalk or 3M4200 (I try to stay away from 5200 whenever possible) always seems to do the trick, an avoids using screws. Although sometimes a carefully placed, very small, screw can be OK.
Aesthetics... that's a personal thing. Here's another link to various trim pieces - I didn't look closely to see the sizes, though:
https://www.mcmaster.com/#trim-molding/=16c6f79