Plastic! Bah! Humbug!!
Actually, Steve D's recommendation is pretty doggone good one, but there's another possible way -- more expensive, yes -- but it depends on how much you love your boat and how long you plan on keeping her.New Found Metals has replacement bronze/brass and stainless steel ports at pretty reasonable prices. If you are not a do-it-yourselfer, plan on spending at least as much on installation of the ports by a yard as you spend on buying them, so effectively double the cost. And, of course, you don't have to do all of them at once; a few at a time as you can afford it is a good idea. That's going to be the next big project for mine.Well, this is just a thought.