Colts and Springers ship with 7 round mags. That's just how they are.
Any 7 or 8 round magazines will work fine with your gun, and since it has a steel frame, it'll be safe with "devel" style followers like you see on CMC mags.
Any type Wilsons or Chip McCormick mags will be fine. The Wilson mag nomenclature is confusing, but there's essentially the standard "47" type and the ETM "500" type in 8 round flavors, the different variants are essentially what kind of base pads you can put on them.
I shoot Wilson 8 round mags in all of my SA guns.
OK, so not all plastic guns are bad