I would probably doubt that there are still any SlingShots out there that have not yet been modified, but just for FYI I did find somebody selling these kits. The asking price is more than the original kits originally sold for, but it is still cheaper than buying the parts separately.
This kit is for the 2016, the 2015 kit included a smaller battery as used in current models to offset the weight of this kit. (We did add the muffler heat shield to our 2015, but not the radiator shroud nor the battery.)
I apologize that this is from one of the other forums, but for nostalgia, here is more information of what we were experiencing back in the day this kit first was introduced: