On most assemblies, the cable goes through a hole in the shoulder end and is secured back on itself with a compression fitting on the cable. It is more or less permanent unless you cut the cable.
A similar loop is formed in the other end of the cable once the proper lenght is determined. The cable is then run through the corrogated hose and the end of the corrogated hose is pulled back enough to allow the end of the cable to be secured to the power inflator with a pin running from holes in each side of the inflator through the loop.
After this is secured, the corrogated hose is fitted over the inflator and once the inflator properly oriented in the direction you want it to face, it's secured with a pair of zip ties.
You could extend this with a fishing leader but it, or at least the ends of the leader, are not as strong as the rest of the cable itself. You should be able to find SS cable and the swaged fittings at the local hardware store and then replace your old cable with a longer one piece replacement.
The other issue with using a leader to extend the cable is that the difference between too short, just right and too long spans a range of about 1". If it's too short the corrogated hose is compressed and unintentional air loss will occur. If it is too short, the hose gets stretched more than is needed and dumping air will be harder than is desireable - plus hose life will suffer.
