It is not right to make copies from other photographer's work even though you have paid for the finished product but not their intellectual property.
but for this case is more like a novelty item than a portrait work......
Yes, just use a flatbed scanner is the most cost effective,
however, whatever methods you use, degradation of the quality is inevitable for making duplicate copy,
if you have a poor quality original, you decide whether it is worth the time, efforts and costs to reproduce it.