A friend of mine swears by weed eater line from Ace Hardware, says it handles better than the mono. Myself, I already bought a big spool of the 400# mono so that's what I use. Is it invisible? No... but I think it's less visible than black or green PVC or rope.
I hate wrapping decoy cord so much I even Texas rig my hand carved blocks, I do store them in a slot bag though, just don't spend any time wrapping line.