Get the map from the NCR Rangers, for Vortis the slaver
Aid the slavers
Rangers' map location
Let me tell you, then. These Rangers have got it in their heads to wipe out slavery and slavers - by force. They've been creating a lot of trouble for hard working folks.”— Vortis
As the NCR Rangers are a threat to slaver operations in Northern California, they would do anything to hamper their operations. The slaver Vortis from NCR looks to procure the Ranger map from their headquarters in the downtown NCR area and the Chosen One can provide him with it, for adequate compensation - $500.
Go to the Ranger's base downtown, south of New California Republic (town). You and your party must hide your weapons to get through the gate. Head south-east and behind Sheriff's office, you'll find a building with a garage inside. In the room with a workbench, search the table in the left corner. Take the map and return to Vortis.