Old seasonal armour used to be in his loot pool and could drop randomly from rank up engrams or strange weapon engrams. When EoF launched, old seasonal armour was moved to Ada. Neither of them have had everything though, unfortunately.

Some seasonal weapons/armor sets were moved to the weekly exotic missions. I havent run one recently, but they had the exotic missions drops linked to that seasons armor set and red border craftable weapons. This was through the planets menu, not portal. I just read an article, post Edge of Fate that it was still the case. This might get you some of the older gear Also I think Dares of Eternity has some older armor and weapon loot pools. Someone can correct me if im wrong, but worth a shot.