I googled and couldn't find a list of what's added by the BG2 Tweaks Exotic Items Pack anywhere, so I traced through the WeiDU install and made my own list. I figured I should post it somewhere to save everyone else the trouble and at the same time, probably also answer a lot of the questions I saw when googling that went something like "Is there/Where can I find <x> in the Exotic Items Pack?" Given that this is based on tracing through code and not on in-game verification, it's possible that there are mistakes or things not obvious in the coding, but this should be fairly accurate.
Scrolls
Contagion - Davaeorn (Cloakwood Mines, Level 4)
Find Familiar - High Hedge; Sorcerous Sundries
Hold Undead - Sorcerous Sundries
Melf's Minute Meteors - Sorcerous Sundries
Power Word: Sleep - High Hedge; Sorcerous Sundries (not available in v10, v11)
Protection from Cold - Sorcerous Sundries
Reflected Image - High Hedge; Sorcerous Sundries
Spider Spawn - Sorcerous Sundries
Spook - High Hedge; Sorcerous Sundries
Ioun Stones
Deep Purple Ioun Stone (60' infravision) - High Hedge
Flickering White Ioun Stone (10% cold resist) - Davaeorn (Cloakwood Mines, Level 4)
Weapons
Katana - Meilum (Firewine Bridge)
Katana +1 - Haseo (The Hidden City)
Katana +2, Tsu-O-Shi (cursed - see below) - Krumm (Area SW of Nashkel)
Ninja-to - Flesh golem cave (Lighthouse)
Ninja-to +1 - Black Lily's store (Baldur's Gate Thieves' Guild)
Scimitar - All stores that sell short swords
Scimitar +1 - Maneira (Exit from Nashkel Mines); Sendai Argrim (Area S of Nashkel)
Wakizashi - Hakt (Bandit Camp)
Wakizashi +1 - Desreta (Baldur's Gate Harbor)
Ammunition
Bag of Plenty (unlimited sling bullets) - Nashkel Store
Case of Plenty (unlimited bolts) - Thunderhammer Smithy
Quiver of Plenty (unlimited arrows) - Carnival
Stores
Alvanhendar in Gullykin now has one.
As for the cursed Katana +2, it's a Katana +2 alright, but it has a 5% chance each of permanently lowering one of your ability scores by 1 or your max hp by 5 each time you hit. In other words, that's a 35% chance that something bad will happen. If you choose to wield it, you'll be a vegetable in no time flat.