Yamaha used to carry them, but now I heard they ran out of it and will not be ordering any new ones just yet. I suggest you order it online, it should cost about $350 for the 101s and about $500 for the 401s.
I just re-read your post again, and it seems like you already have the sustainer. You can actually go to Guitar777 to install those. Im just not too sure how much. I'm guessing about 50bucks?