DonZ, with regards to CIP newly manufactured ammunition I know of only one option, which should be available through your local rifle smith:
Dorfner ammunition, from Vienna (Austria), see https://www.waffen-dorfner.at/seltene-buchsenpatronen/ . Excellent ammunition that I use for all the range of MS proprietary calibers. In case you couldn't find a rifle smith willing to import them in Stuttgart, I could put you in contact with my supplier in North East France (Alsace, near Strassburg, not such distant from your location) that may supply. Dorfner 9,5x57 MS come in 17,5 grams Teilmantel; c. Euro 110 or 120 per box of 20 rounds.
Good luck with your hunt in Poland.
Louis