Islands for the Ironclads

I quite like these with the squares for gun batteries and forts

And they come in sets of three!

I need some coastal terrain for my 1/2400th scale ironclad scenarios so have been searching for something off the shelf to save me the time and effort of scratch building. So far, all that I've been able to locate are the vac form pieces produced by Amera, which while not too expensive aren't really what I'm looking for, as I need some long stretches of coastline rather than islands. I think I'll just have to dig out some high density foam and get carving away to recreate a scenic bit of Brittany or the Baltic.