Try the monsters in the Cavern of the Discarded, which isn't really a cavern. Rather, it consists of the three campsites of the ratmen-like creatures to the east (more or less) of where you find Sutek in the right half of the Abyss.
While you're there, be on the lookout for other useful imbuing ingredients such as Crystal Shards, Arcanic Rune Stones, Unbalanced Scales (which seem to be called Delicate Scales now?), Abyssal Cloth, Reflective Wolf Eyes, Crushed Glass and Elven Fletching. (Thanks to Crysta for this information.)
Also examine any random loot you see laying on the ground. It brings a whole new meaning to the old saying, "One man's trash is another man's treasure," especially if you're part-rat, or should I say "pack rat"?