For the KC-02, fitting a stock meant for a Ruger 10/22 isn't very hard. Two thing to know, you have to modify the receiver in a pretty permanent way and second, you need a stock meant for a .920" bull barrel as the KJW outer barrel doesn't taper off.
Here's mine with an Hogue Overmolded for .920" bull barrel. The receiver has a rear mounting to the KJW stock that needs to be cut off. Otherwise only some light filing and sanding to both the receiver and stock are needed for a snug fit.