the only one I am aware now making 9x57 is suedeutsche hülsenmanufaktur https://huelsenmanufaktur.de/de/produkte but I dont know if there is realy a correkt headstamp on the brass.

if you ask me ... buy norma 9,3x57 brass, sometimes older 9x57 rifles have a small chamber and accept only brass with +/- 11,80 mm base when most modern brass is more 11,95mm. norma brass have this smaller base and the quality is simply top.
think you get it in the united states.