It's aftermarket, that's the Rod Millen kit, I think. That was one of the few options when the Capri was relatively new.
No factory body kits to speak of, the 94 XR2's got sideskirts but that's it.
I've only seen a handful of them through the years, not very common. Millen also had a bubble top, I believe he sold the molds to Kaminari who still make them. None of the other bits are still made as far as I know.