Soldiers!
Should you spot carrion collectors travelling the road while on your patrol, let them pass. Do not talk to them, do not ask questions. Rest assured they're doing the Knyaz's bidding.
Orders Regarding Carrion Collectors
Orders to Brencis's soldiers.
Where to get it
From the game's own loot tables and the inventories its characters carry. A percentage is the highest spawn chance recorded for this item; a row without one always carries it.