Whispers of Silence

You can get this cloak from a Tasloi in Cloakwood Forest and bring it back to Gurke at the Jovial Juggler in Beregost. However when you bring this cloak back, he doesn't want ik back, because when he gets it back, he cannot be a tourist attraction any longer.

In-game description
"Cloak of non-detection: 'Whispers of Silence'. Reportedly created for a lineage of the greatest burglars ever to walk the night, this cloak was a apparent success. No record exists of previous owners"