Defender industries should have something. 3/16" is big enough, some manufacturers sizes vary a little bit. Nylon shrinks and expands too much. Marlow has a real nice polypropelene braid (it's standard on P&H boats) but it doesn't seem to come in black, there's yellow and some other colors, there's some inexpensive polyester yacht braid (I think that's what Necky was using for a long while) , the 1/4" polypropelene rescue rope is kind of pricey.