You can find Shadowed Men for the drops in most zones of Norrath. A good spot is The Obelisk of Lost Souls. Another spot is to the left as you leave the beach in Nek Forest.
Just a little hint...I had a hard time getting the updates off of many of the shadowman that I could find but seemed to have no problem getting them from "a shadowed soulflayer" and "a shadowed soulcrusher" (these are low 40 mobs) in The Obelisk of Lost Souls which is found in Feerrott.
Although there are only a few mobs in The Obelisk of Lost Souls and there are not enough to get all 10.
Drops also on Shadowed Man Invaders in Nektulos, Lesser Faydark, Shadow Grove, you have to kill a lot, but they drop.
found in Stonebrunt Highlands
They also drop off the Theerian blademaven in Highlands as well as shadowed men L&L items.