Do a little research and track down the dealer TSB on the brake systems. The TSB lists all part numbers for GM OE parts, including the PAIR plus the main cable (instead of three transactions, the left and right could be bought together). I went this route and scored all 3 cables, NOS, on eBay, from sellers who didn't even know what they were for. Paid less than $50 shipped. Main cable included the clip. You may need to locate an equalizer though I believe dorman makes one. I believe the TSB was for the faulty clutch mechanism in the rear calipers and covered cable replacement if necessary. Next step? Replace rear calipers. The ebrake always failed because people didn't use them enough. New cables won't likely give you functional ebrakes. Best of luck!
The car I got did not have any cables passed brake lever. If you have ANY spare cables for ANY part of the system I will buy them and pay shipping!
What year is your car? The cables are different for 88. I had an 88 for 12 years. I always bought AC Delco cables. I have a left and right on my shelf waiting to go on my current car.