to get aditional metal coat's i've devised this method, note* this can be used for other items on wild pokemon with other items aswell.
to obtain additional metal coats than the one found in the pokeball factory find a pokemon with the frisk ability and teach them the TM thief, this is found in the upper right house in camphire town, after that go to the lost hotel and run around until magneton shows up, idk percentiles but the frisk ability will tell you if they have a metal coat or not, you can either catch them or use thief to obtain the metal coat. be careful cause if your pokemon is holding an item thief cannot be used. personally i use noibat that had frisk when i caught it but there are others out there. i hope this helps!
to obtain additional metal coats than the one found in the pokeball factory find a pokemon with the frisk ability and teach them the TM thief, this is found in the upper right house in camphire town, after that go to the lost hotel and run around until magneton shows up, idk percentiles but the frisk ability will tell you if they have a metal coat or not, you can either catch them or use thief to obtain the metal coat. be careful cause if your pokemon is holding an item thief cannot be used. personally i use noibat that had frisk when i caught it but there are others out there. i hope this helps!