Jon,
I used to use Top Shot dacron because it came in black, was nice and waxy to prevent rot and also low-viz.
It's hard to get now, so I normally use black dacron from Black Pete Marine. They are a distributor so you would need to get it through a tackle shop. It's readily available.
The Black Pete dacron is not as tight a weave as the Top Shot, though I haven't found any real issues with it. I use it all the time now in the lighter 50 and 80lb classes for light tackle billfish and jigging wind-ons........never had it fail so I will keep using it!
Aaron.