You don't scan PRINTS. You scan the negative or transparency and provide an accurate description of the media to which it is/will be printed.
That is usually quite sufficient for prospective clients. If more is required, visit them or have them visit you to view the work on the media it is printed to. Relying on scanners to do this for you is foolish and unrealistic — the representation in any shade of "accurate" is not going to come through.