Compiled by me with reference to several walkthroughs.

Disc 1

G.F Name Elemental Found at Attack

Quezacotl 

Thunder Tutorial desk Thunder Storm
Shiva Ice Tutorial desk Diamond Dust
Ifrit Fire Fire Cavern Hellfire
Siren None Draw from Elvoret (Boss) at Dollet Communications Tower Silent Force
Brothers Earth Tomb of the Unknown King (defeat the Brothers) Brotherly Love
Diablos None Magical Lamp from Cid (defeat Diablos) Dark Messenger
Carbuncle None Draw from Iguions (Boss) Ruby Light (casts reflect)

Disc 2

G.F Name Elemental Found at Attack
Leviathan Water Draw from NORG (Boss) at Balamb Garden Tsunami
Pandemona Wind Fujin and Rajin (Boss) Tornado Zone
Cerberus None Main Hall of Galbadia Garden Counter Rockets (casts Double & Triple)
Alexander Holy Draw from Edea (Boss) in Galbadia Garden Holy Judgment (drives elemental weakness onto enemy

Disc 3

G.F Name Elemental Found at Attack
Doomtrain Poison Requires Solomon Ring at Tear's Pt. in Esthar plus additional items Runaway Train
Bahamut None Deep Sea Research Center in SW corner of world. Must answer some questions correctly Mega Flare

Late in Game

G.F Name Elemental Found at Attack
Jumbo Cactuar None Cactuar Island 1000 Needles
Tonberry King None Defeat a certain no. of Tonberrys at Central Ruins, then defeat Tonberry King Chef's Knife
Eden None Defeat Bahamut at Deep Sea Research Center. Head underwater, encounter Ultima Weapon then draw from it. Eternal Breath