I agree that it's easy enough to just use some extra line you might have around for a ridegeline, provided that it is strong enough.
But, if you are looking for something specific to use for a ridgeline, then you could do worse than this
. It's very light, has a small diameter of 3mm, has a vectrus core tensile rating of 653 lbs, and it's polyester sleeve should knot well. Seems ideal to me.