It really depends on what the problem is? If it is simply a jammed sensor due to a paper jam you may be able to floss out the problem by using a stiffer piece of paper to push out any remaining blockage. Bear in mind that you must only push the paper through in the normal direction of travel to prevent breaking paper sensors. If something is broken there are few, if any parts available and in the case of a dead ADF finding a used one on Ebay is likely the only solution.
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