Aeroga is available in Archades.

Most of the best weapon can be gotten in Bazaar, here are some that I know:

(SPOILER)Top 10 Best Attack Power:
1. Zodiac Spear (ATK +150) (Spear)
-Necrohol of Nabudis (Special)
-Henne Mines (al-bhed_kid0827, you get a deadend when you enter from Feywood!)
2. Tournesol (ATK +140) (Greatsword)
-Bazaar, Serpentarius x3, Empyreal Soul x3, Gemsteel x3
3. Wyrmhero Blade (ATK +130) (Greatsword)
-Bazaar, Omega Badge x1, Lu Shang Badge x1, Godslayer Badge x1
4. Excalibur (ATK +126) (Greatsword)
-Great Crystal, Roadway to Ultima
5. Scorpion Tail (ATK +119) (Axe)
-Bazaar, Charged Gizzard x3, Wyrm Bone x3, Scorpio Gem x4
6. Ultima Blade (ATK +118) (Greatsword)
-Bazaar, Adamantite x2, Death Powder x2, Gnoma Halcyon
-Pharos - Subterra B1F
7. Golden Axe (ATK +110) (Axe)
-Dalmasca Estersand (After Ridorana)
8. Ragnarok (ATK +109) (Greatsword)
-Reward for Rank VI, Elite Mark, Ixion
9. Whale Whisker (ATK +108) (Pole)
-Bazaar, Mythril x3, Corpse Fly x3, Aquarius Gem x4
10. Greataxe (ATK +101) (Axe)
-Bazaar and I don't know what the ingredient is.

Other Weapon:
Dagger: Danjuuro +80
-Drop from rare game, Larvae Eater (Great Crystal)
Ninja Sword: Yagyu Darkblade +80
-Drop from rare game, Bombshell (Lhusu Mines)
Gun: Fomalhaut +50
-Treasure in Lhusu Mines, Cerobi Steppe, Henne Mines, Pharos Subterra
Handbomb: Volcano +85
-Reward for Rank VI, Mark, Catoblepas
Crossbow: Gastrophetes +76
-Steal from rare game, Pallicant (Ridorana Cataract)
-Outfitter in Phon Coast
Mace: Grand Mace +72
-Reward for Rank VII, Mark, Pylraster
Measure: Euclid's Sextant +35 (Hit: Bubble)
-Reward for Rank VI, Mark, Wild Malboro
Rod: Rod of Faith +24
-Mt. Bur-Omisace, clear Rank VII, Elite Mark, Behemoth King and unequip Vaan's weapon, punch the wyrm-like face in Mt. Bur-Omisace,
you'll also get 500000 gil.
Staff: Staff of the Magi +44
-Steal from rare game, Luxollid (Pharos Subterra)
Bow: Sagittarius +93
-Bazaar, Beastlord Horn x3, Moon Ring x3, Sagittarius Gem x4
Sword: Durandal +99
-Bazaar, Lifewick x3, Emperor Scale x2, Leshach Halcyon
Katana: Masamune +93
-Bazaar, Gemsteel x2, Mallet x2, Orichalcum x2
-Reward for Rank VII, Elite Mark, Ancient Man of Mystery
Spear: Dragon Whisker +91 (In case you don't want the Zodiac Spear)
-Treasure in Pharos Third Ascent, Cerobi Steppe

You can see Pole, Axe, Spear and Greatsword in the top 10 best attack power.