A number of years ago I discovered Prvi Partizan,which has slowly but steadilly been gaining fans ever since.I originally started using it as just "shooting" ammo at the range ,because it was so economical.Eventually,I started reloading the brass and found it to be excellent.They make a wide variety of the metric loads and do sell unfired brass.You might want to try Buffalo Bore or Graf Bros. for availability.
I also bought a 7x57 trim die from RCBS many years ago,and never considered it that big a deal to make my own 7x57 from 30.06,.270,or .280 among others.I have then often turned around and used those cartridges to create 6.5x57,.257 Roberts,and even 6mm Remington,though those did require neck reaming and annealing ,it was fun,and saved me quite a bit of money.You really don't have to make THAT many at any one time to keep you shooting.
I've also successfully made 9.3x57 by successively necking up 8x57 ,first through a .35 Remington die (pushing the case in until it just slips over the expander),then the 9.3x57.