A local store has unpasteurized apple juice but it has potasium sorbate added.
Can something be done to use this or am I just out of luck?
I wouldn't have much hope of getting around the sorbate myself. You could try to ferment a small amount and see if it works and if it does, make a bigger commitment.
You are much better off finding pasteurized juice with no preservatives rather than unpasteurized juice with sorbate.