Now this is only what I've observed, but it's not too hard to see, just pull the grill off a V-Dosc and you can see the upper and lower portions of the central "flare" area are just the flat outer panels of the box itself. Some don't even have top and bottom panels forming a flare (the Outline boxes for example).
The "magic" seems to happen in the patented assembly that couples the driver to the flare and I doubt there's going to be any of those sold a-la-carte! You could probably source Chinese clones, quite possibly of the L-Acoustics part as it's old enough that patent protections may have lifted by now (not that that has ever really stopped some China companies!)
Also after looking over most line-array products out there, the 400/500Hz-and-up range seems to be done with cone drivers.