Actually, in 2e fighter/mages can wear any armor they want... they just can't cast spells in it (unless it's elven chain or elven plate.)
Bracers of Armor are considered a good investment after a while, but at low levels there's the level 1 spell Armor, which gives you an AC bonus of... either 4 or 6, I don't recall right offhand, but anyway, it lasts 8 hours. Keeping one or two memorized at low levels is a good plan.
At higher levels... I can't recall the name or the book it's in, but I could swear there was a magic item that let you send one piece of equipment to a pocket dimension and resummon it, equipped, at will.