All you need is a set of 9x57 dies and some 9.5x57, 9.3x57, 8x57, 7x57, 6.5x57, or 6mm Rem brass - and a loading press, of course. Dies and the press to do this light case necking are cheap. I hesitate to sae case forming as necking 8x57 or 7x57 brass to accept a 9mm bullet is as easy as running the case into the FL die and out - done - either is now a 9x57. Since you live in the States, I'd merely use 8x57 RP brass and a set of Hornady or Lee dies.

Actually, you could do all your loading and necking with a set of .358 Winchester dies - probably - about $35.00 for the dies.