Where to buy the hydra in GTA 5?

Could you please elaborate on where one might be able to purchase the "hydra" in Grand Theft Auto V? Is this a specific vehicle, weapon, or item that's available within the game? Are there any specific requirements or missions that need to be completed before it becomes accessible? Additionally, are there any in-game stores or locations where this item can be found, or does it require a certain level of progress or achievement? Understanding these details would help us provide a more accurate answer to your question.