How to find Items for Upgrading Weapons
Here is where you can find all items necessary to upgrade weapons. When I say that a monster drops an item, you must not mug the monster for it to drop that item. In brackets, the area where the monster is found. If, for example, no Card-Mod is shown, then the item can't be obtained in that way.
M-Stone Piece
Dropped by: Bite-Bugs, Glacial Eyes (on the island where Balamb Garden is found.)
Mug from: Bite Bugs
Card-Mod: 1 Bite-Bug -> 1 M-Stone Piece; 1 Funguar -> 1 M-Stone Piece
Screw
Dropped by: Geezards (the island where there is Deling City, Dollet etc.)
Mug from: Geezards
Card-Mod: 1 Geezard -> 5 Screws
Fish Fin
Dropped by: Fastitocalon-Fs (all beaches)
Mug from: Fastitocalon-Fs
Bomb Fragment
Dropped by: Bombs (Fire Cavern)
Mug from: Bombs
Card Mod: 1 Bomb -> 1 Bomb Fragment
Spider Web
Dropped by: Caterchipillars (forests near Balamb Garden)
Mug from: Caterchipillars
Card Mod: 1 Caterchipillar -> 1 Spider Web
Steel Pipe
Dropped by: Wendigoes (forests near Timber, brown areas near Deling City, D-District Prison)
Mug from: Wendigoes
Card Mod: 1 Elastoid -> 1 Steel Pipe
Dragon Fin
Dropped by: Grendels (Island Closest to Hell; you will fight one in Balamb Garden after the Missile Base sabotage)
Mug from: Grendels
Card Mod: 1 Grendel -> 1 Dragon Fin (this is really the only way to get a Dragon Fin early in the game.)
Mesmerize Blade
Dropped by: Mesmerizes (Centra area)
Mug from: Mesmerizes
Card Mod: 1 Mesmerize -> 1 Mesmerize Blade
Shear Feather
Dropped by: Thrustaevises (island where there is Dollet, Deling City etc, D-District Prison)
Mug from: Thrustaevises
Card-Mod: 1 Thrustaevis -> 1 Shear Feather
Magic Stone
Dropped by: Level 20+ Bite-Bug (island where there is Balamb Garden)
Mug from: Bite-Bug
Card-Mod: 1 Buel -> 1 Magic Stone; 1 Grat -> 1 Magic Stone; 1 Jelleye -> 1 Magic Stone;
Sharp Spike
Dropped by: Grand Mantis (Deling City Sewers), Death Claw
Mug from: Grand Mantis, Death Claw
Card-Mod: 1 Grand Mantis - 1 Sharp Spike; 1 Death Claw -> 1 Sharp Spike
Betrayal Sword
Dropped by: Forbiddens (Centra Ruins, Ultimecia's Castle)
Mug from: Forbiddens
Card-Mod: 1 Forbidden -> 1 Betrayal Sword
Turtle Shell
Dropped by: Adamantoises (Long Horn Island, NW of Dollet; beaches near Shumi Village)
Mug from: Adamantoises
Card-Mod: 3 Adamantoise -> 1 Turtle Shell; 2 X-ATM092 -> 1 Turtle Shell
Dragon Skin
Dropped by: Level 20+ Anacondaurs (forests near Timber, Dollet)
Fury Fragment
Dropped by: Ruby Dragons, Blue Dragons, Grendels (Island Closest to Hell)
Mug from: Blue Dragons
Card-Mod: 4 Blue Dragon -> 1 Fury Fragment