http://www.lampsplus.com/products/marlex-nautical-13-inch-high-white-outdoor-wall-light__3d435.html

I would say (in my expert opinion) you don't want to go with anything white. If it is white, it has been painted, and will likely deteriorate, fade, or chip over time. Why not go with a simple copper fixture? Copper and brass do not rust in the salt air and will last a lifetime. You might save a little with a cheaper light today, but you'll have to replace it within a few years. Our light fixtures come with a lifetime warranty and start at about $250! Please let us know how we can help! www.lanternandscroll.com or buyfrom@lanternandscroll.com Cheers!

Also check out Coastal Source: http://www.coastalsource.com/architectural/

They're a product line I really dig. They're based in Key West and designed specifically to withstand harsh environments (like the coast). They're a little spendy but I've drank the Kool-Aid (and I don't even qualify to be a dealer).