I am not aware that such a kit exists. If there is a legitimate knock to made against the Kymco side by sides, it is that aftermarket accessories are few and far between, especially relative to what's out there for Hondas, Yamahas, Can-Ams, Polaris, etc.
So, if there aren't many places making things such as roofs and windshields for these machines, you can imagine that offering something such as a power-steering kit would be quite unusual.