The entrance to the raider hideout is found on the drainage pipe by the pond. On your first visit, you’ll find Tweez and Bear guarding the first outpost. Kill them and find the issue of Tales of a Junktown Jerky Vendor on top of a barrel.
Further inside, you’ll find Walter and Whiplash. Kill them and loot the Gift Shop Key from Walter’s body. You can use that key to open the safe in this room. The unique weapon Big Jim is also found on the table beside the shelves.