This is most easily obtained in the level The Crossing. After crossing the first patch of ice, before going up the stairs, there is an area with a large dead Demon where you will be ambushed by Watchmen. The corpse with no legs resting against the bridge support has a Helsing next to it. Proceed up the stairs and through the next Watchmen ambush inside the ruined station. Move up the stairs, through the gate, and up another set of stairs to a hall with a brightly lit doorway at the end. A flying Demon will pass by but another Demon perched on the railing will turn and roar at you before taking flight. This Demon can be killed with one shot from any weapon, it is not even necessary to pump the Helsing.
It can also be obtained in the level The Dead City. There is a Helsing early in the level that you can pick up, with enough ammunition to kill it solely using the Helsing, should you wish. Once you climb the ladder, a Demon will attack you. On the roof, it will circle and generally leave you alone unless you attack it or go near its baby. Note that killing this Demon counts toward the bad ending. You can get this in chapter select if you are working on the good ending. Below is a video guide if you are having trouble.
- The name Van Helsing is a reference to the famous fictional vampire/demon hunter, Abraham Van Helsing from Dracula.