The cord I've used in previous years has been fine, although unfortunately I can't for the life of me think where I got it - it was probably either somewhere locally that I'm not likely to be able to get to, or already in my stash. It's just last year's that has worn badly - it looks as though the colour didn't go all the way through, or it faded really badly, and then it wore badly as well, which looked even worse.
The Prym cord says it is "completely dyed, light-resistant, water-resistant" which sounds like a good start.