Heres everything i can think of after a look at my last playthroughs notes in order of appearance :
No Encounters Weapon from Geosengo (Baaja Temple)
Magic Counter Buckler from Mobile Agency Shop (Calm Lands)
0-Slotted Longsword (if sold) can buy it in Macalania Agency Shop until getting the airship (Macalania Lake)
PRIMERPrimer XIX (Bevelle)
PRIMERThe Equipment dropped from fiends underwater in the Via Purifico in Bevelle is appently impossible to find or create by any other means
Primer XX (Home)
PRIMERPrimer XXI (Home)
PRIMERPrimer XXII (Home) *compilation sphere will save you if you have another savefile or do a new one
Magic Counter Buckler from Mobile Agency Shop (Calm Lands)
Wantz (merchant) Apperances on Mt Gagazet & Macalania Woods
Durren (blitz player) Leaves after entering Sin (Calm Lands Gorge)
No Encounters Weapon from Geosengo (Baaja Temple)
Weapon drops with +10% Critical Bonus from Penance (Monster Arena)
Farming Dark Yojimbo (dont kill him the 5th time)
Master Sphere's from Dark Aeons/Monster Arena ect are technically limited
The Equipment dropped from fiends underwater in the Via Purifico in Bevelle is appently impossible to find or create by any other means
DakrDark Aeon interfearanceinterference :
Besaid DST/Fayth chamber, Jecht Sphere #1, Energy Blast Overdrive(Overdrive), Viluca(blitzplayer) , PRIMERPrimer II (Blocked by Dark Valefor)
Macalania DST/Fayth chamber (blocked by Dark Shiva)
Sun Crest (Zanarkand) (blocked by Dark Bahmut)