Looking at the cards, the screws seem to be in the same places and what features you can see of the 280X PCB are similar to the 7970 model. I dont know for sure, but I think it would fit. You might need some rubber washers to add a bit of room between cover and PCB though, they might have changed something about the 280X PCB to lower its height or something.
No idea where you could get one, suspect the only way to get one other than buying a Vapor 280X would be off someone else.
yeah I just looked at them and the screws seem to match. The only screws that don't are the ones holding that little piece of plastic that's supposed to keep the card from bending on the 7970. Maybe in a couple of months after more of these are sold it could be possible to get one from ebay. We'll see