Making your own pectin for your fruit preserves

I have been unable to find commercial pectin in any of our supermarkets when it is time to make jam, but, I have found an apple pectin recipe which does the job. The recipe calls for sour cooking apples, but I have used normal eating apples, both red and green, with no problem.  Even those forgotten apples from the bottom of the vegetable drawer in my fridge - those no-longer-crisp, flowery