this bluse is definitely not NPEA, I rather think AHS. It is not common and hard to find in this condition.
Plastic buttons do not bother me. I also think that this item is genuine but not for me because I can not collect everything for the reasons you already know.
there has been a set of 12 postcards from Sonthofen. One of them shows this uniform and it still misses me in my collection.
You will perhaps be lucky enough to find it in Germany.