I have tried farming these in Gendarran Hills by killing centaurs which I came upon across. From the Light Bags they dropped and salvaging any Acolyte equipment I now have around 160 of these in around 6 hours. I know it might not be much, but so far this is the best I have found.
Also sometimes salvaging the Acolyte equipment yielded cotton scraps and have around 50 of those in the meantime as well.
I tried the bandits in Kessex Kills, south west of Viathan Lake, but was scared away by the stationary cannons that can't be harmed.
Another recommendation I read somewhere are the pirates in Gendarran Fields around Brigantine Isles, but I was not impressed by the results there, either.
In general: Most wool scraps are not dropped directly, but contained in salvageable items. This seems to be true for all scraps.
Where would be a good place to farm this?