I was editing the title when my phone glitched and posted.
Anyway, my favorite coated cable ever is the RPM, but I don't know what cable/coating they use. It's too pricy for general class purchase. Jump N Rope has a reasonable rope for $35 /100 ft and it's a nylon coating which is what I was leaning toward. I'd still like to find a good cable supplier though.
It looks like the same type of cable is available for like $10/100ft if you just buy coated cable rather than from a jump rope company, but you have to know the right specs:
http://www.amazon.com/Loos-Galvanize...n%3A3377239011 WFS