He just needs to use 1/2" Stable Braid or other full poly line. It's going on a capstan winch, up to 2klbs working load.
Since he said "small" and 1/2" isn't his variety of small, you could get by with 3/8". Here's 150' from the rope guy for $75. I'd cut it into 50 and 100 methinks. 5600ABS...