The Huntress Boltcaster is one of the most useful weapons in Prey. It can serve as a distraction, or be used to trigger buttons or computer screens that you cannot reach.
You can find this in the Sales Division of the Talos I Lobby. This is on the third floor, and its the same destination as the "Stolen Neuromods" side mission. If you don't have Leverage III at this point (which you probably don't), you'll have to access the Sales Division a different way.
From Morgan Yu's Office, break the window looking out over the Talos I Lobby and stand on the platform outside. With a bit of a running start, run and jump to the hanging structure on the side. You can use this as a bridge that will take you to the other side of the third floor. Once across, turn right and enter the Sales Division.
Inside, the now-Phantom version of Yuri Kimura, so you'll need to kill Yuri. In the back of the office, there will be two desks. Yuri's desk will contain the stolen Neurmods. The desk opposite of Yuri, still at the back of the office, will have the Huntress Boltcaster on the floor.