You are getting close to the level of getting items with +stealth. There used to be a great compendium of what these are and where they drop on the forums. Not sure if it still exists. But I know there's a few skirm camp items (I know you're not quite there). But definitely pick up +stealth pocket items and cloaks when you can to help with this.
Parahelion - Burg, Krustii - Champ, Shurmann-Cappy, Tommac-Min, Lazarrus-LM, Thromdir-Hnt, Theodolan-Grd, Kozzmeaux - Bear - Dancing in the Dark kinship.
Wrecks - Warg - The Black Blade