I don't think there are any plastic kits available. I read about someone doing a vacuum-formed kit, but apparently that fell through.
The Halo is an amazing machine. I'm a CH-53E guy, and that's a huge machine. However, the Halo is a monster. It dwarfs the 53. I got a chance to see one at a distance in Djibouti, Africa about a year ago. That thing landed like a big white whale. It made a ton of noise on approach. It sounded like John Bonham playing the drums. Once the wheels touched deck, they cut power on one of those big 13,000 hp turbines, and it taxied in on a whisper. It was cool.
Apparently, they need a long approach path to land, so it's doubtful that one could land on a rooftop, even if there was a rooftop big enough for it. But I think that diorama would look cool.
Semper Fi,
Chris