Rear Seat Knobs

I was trying to push my rear seats down to make more room in the back. (A feature I have not used in a few years) I start to pull up on the knob and it immediately breaks off (with very little force). I then repeat the procedure on the other back seat and the knob immediately breaks off (again with hardly any force). Now I can no longer bring my rear seats forward. Does anyone know what is involved in replacing the rear seat knobs and where I would find the necessary parts?