There's a centre cable that connects to the handbrake, then there are 2 more cables (left and right) attached to the centre cable under the middle of the car, and they go off to each rear wheel.
The left and right cables are identical, except for the mounting brackets (they come with new brackets which are different on each side, but you can keep the original brackets anyway).
I bought brand new left and right cables from my local Toyota dealer with no trouble at all.
I didn't need to replace the centre cable on mine, and I think it's always the side ones which have issues. In my case, the right side cable was seized but I replaced both sides.