Correction. Magazines for the No 1 rifle wil not fit into or lock into the No4 correctly, its much worse than "feeding issues".
Try what we call "the usual suspects". Sarco, Springfield Sporters, or Numrich.
You should find real issue magazines for between $25~35.Don't even think about the el cheapo repros & copies they're horrible.
Chargers I usually find at local gun shows, but avoid the rough parkerised finish ones as they are very hard & gritty to operate.
Allan Quatermain: “Automatic rifles. Who in God's name has automatic rifles”?
Elderly Hunter: “That's dashed unsporting. Probably Belgium.”