Wolf is correct, I have the RainX cover from Walmart for mine. Size medium I believe. Whatever size a Nissan Altima takes. It will keep the elements out pretty well. At least it did at SSITS. It should fit your wing and just tuck under the tail. On mine without a wing, the back goes all the way to near the bottom of the rear tire. Just be careful with the wing tips when putting it on.
I am pretty sure it was $65-$69.00.
You can buy it and try it, and return it to them if it doesn't fit. One good thing about Walmart.
After seeing how tight the trailering cover was on Rabtech's at SSITS I would say there is no way it will fit a wing. It is shaped exactly to the rear of the slingshot.
Stephen