You could always use an OEM Glock 10-round G43X/G48 magazine, but then what's the point of chopping the G43X/G48 frame.Having to use Shield Arms mags would make it a no go for me.
We'll eventually have a PSA Dagger™ Micro 15-round G43X/G48 hybrid polymer/steel magazine (which works with the OEM polymer magazine release), but again, what's the point of chopping the frame.
Eventually someone will manufacture a grip-chopped G43X/G48 frame. My money is on PSA. Obviously, PSA could cut down their Dagger™ Micro magazine to 10 - 13 rounds. Of course, at this point, there's no reason to think the Dagger™ Micro magazine will be any more reliable than a Shield Arms magazine. Only time (and thousands of rounds) will tell ... assuming the Dagger™ Micro magazine ever sees the light of day.