Can I get the Queen Gambit Gun?

I'm towards the end of the game, and really just looking to get this sniper as a finishing touch... In a View to Kill, I got evidence against Tenpenny, because you know, I wanted to not be heartless 😅

Now, I'm realizing that you can't build the Queen's gun on your own, you can only get it from Tenpenny? He's still there, when I got to his balcony, but he won't dialogue with me, and if I kill him he just has a regular vintage rifle...

I got the messenger to show up, but I received no new quest line from him, and the quest has been shown complete for a long time now.

Any help?