Its... WoD? Legion? thing. Yes, in WotLK one has needed to have 2 separated left handed and right handed models in cases of fist weapons. So you need to take that model and I wouldn't turn it, I would apply one negative scale to it, to get mirrored version. You'll also have to make 2 items, main hand and off hand item.
If you can't do 3D modeling or port stuff into WoW, you are simply screwed and need to learn it to solve this.