Did some searching, all the orc runners should drop the same items -- the idea is that they're couriers between the warrior guild in Neriak and the orcs of Crushbone.
Item id for the Sealed Letter should be 18840 (
http://lucy.allakhazam.com/itemraw.html?id=18840), Runner Pouch should be 13226 (
http://lucy.allakhazam.com/itemraw.html?id=13226). Hope that helps.