Kymco Xciting 500???
(there is no AK 500).
They are not the same. But they might be close enough where it matters for a rider backrest.
The 500 seat is hinged at the front and AK seat is hinged at the rear of the seat.
But IF the rider backrest mounts using the stock rider back pad rods AND IF those are the same on both then it should work. Otherwise I cannot say. I haven't found a photo of the bottom side of the seat pan of an Xciting 500 to compare.