Items:
Note: NPC= non player character
Adamant Orb – Marvelous Bridge (post-game, received from Shadow Triad)
Amulet Coin – Castelia City (received from dancers after battling all three)
Choice Scarf –Castelia City (gift from NPC in Pokemon Center after trading 30 or more Pokemon))
Cleanse Tag – Icirrus City (gift from NPC)
Damp Rock – Route 8 (talk to Parasol Lady west of Tubeline Bridge during the morning – available once per day)
Destiny Knot – Opelucid City (received from NPC in house east of gym)
Draco Plate – Route 13 (requires Surf – from NPC inside house west of move tutor house)
Eviolite – Castelia City (from NPC with Patrat in northernmost building)
Exp. Share – Castelia City (received from Battle Company's president), Icirrus City (pokemon fan club)
Expert Belt – Driftveil Market (from NPC if you show a Pokemon level 30 or higher)
Float Stone – Opelucid City (received from NPC in Drayden's House)
Griseous Orb – Marvelous Bridge (post-game, received from Shadow Triad)
Heat Rock – Route 8 (talk to Parasol Lady west of Tubeline Bridge during the day – available once per day)
Icy Rock – Route 8 (talk to Parasol Lady west of Tubeline Bridge at night – available once per day)
King's Rock – Route 13 (from Treasure Hunter)
Lucky Egg – From Professor Juniper during story when you meet her in
Lucky Punch – Route 13 (Treasure Hunter)
Lustrous Orb – Marvelous Bridge (post-game, received from Shadow Triad)
Macho Brace – Nimbasa City (from NPC in eastern gate)
Magmarizer – Route 13 (Treasure Hunter)
Metal Powder – Route 13 (Treasure Hunter)
Miracle Seed –Nacrene City (from NPC in westernmost house if you answer Snivy)
Mystic Water – Nacrene City (from NPC in westernmost house if you answer Oshawott)
NeverMeltIce – Cold Storage; rarely on wild Crygonal
Protector –Route 13 (Treasure Hunter)
Quick Claw – Skyarrow Bridge gate (from NPC)
Reaper Cloth – Route 13 (Treasure Hunter)
Ring Target – Opelucid City (received from NPC in Drayden's House)
Rocky Helmet – Cold Storage(outside, NCP)
Sharp Beak – Mistralton City (NPC in Cargo Service building),
Shell Bell – Driftveil City (received from NPC in house east of Driftveil Market if you've seen 50 or more Pokemon)
Smoke Ball – Castelia City (from NPC in building across from the gym)
Smooth Rock – Route 8 (talk to Parasol Lady west of Tubeline Bridge during the evening – available once per day)
Soft Sand – Desert Resort (from NPC)
Soothe Bell – Nimbasa City (show a Pokemon with high Happiness to NPC in building north of Battle Institute)
Splash Plate – Route 13 (requires Surf – from NPC inside house west of move tutor house)
Stick – Route 13 (Treasure Hunter)
Thick Club – Route 13 (Treasure Hunter)
Wide Lens –Castelia City (gift from NPC in Pokemon Center after trading 5 or more Pokemon)
Zoom Lens -- Castelia City (gift from NPC in Pokemon Center after trading 20 or more Pokemon)
Master Ball – Gift from Professor Juniper; Castelia City (gift from NPC in Pokemon Center after trading 50 or more Pokemon)
http://www.gamesradar.com/f/pokemon-black-and-white-item-location-guide/a-20110310112141116005/p-2
Evolution Items:
Dragon Scale – Route 13 (Treasure Hunter)
Dusk Stone –Route 10 (from NPC)
Electirizer –Route 13 (Treasure Hunter)
Fire Stone – Castelia City (NPC on easternmost pier if you pick Pansear)
Leaf Stone –Route 6 (research facility if you show scientist all four Deerling forms), Castelia City (NPC on easternmost pier if you pick Pansage)
Magmarizer – Route 13 (Treasure Hunter)
Moon Stone – Pinwheel Forest (from Lenora during story)
Prism Scale –Undella Town (NPC in Pokemon Center)
Protector –Route 13 (Treasure Hunter)
Reaper Cloth – Route 13 (Treasure Hunter)
Shiny Stone – Route 6 (from NPC in healing house)
Sun Stone – Nimbasa City (NPC in building north of Pokemon Center)
Thunderstone – Shopping Mall Nine (received from NPC)
Up-Grade – Route 13 (Treasure Hunter)
Water Stone – Castelia City (NPC on easternmost pier if you pick Panpour)
Misc Medicine:
Lava Cookie – Castelia City (Royal Unova on Mondays, Wednesdays and Fridays)
Old Gateau – Dragonspiral Tower (from Cedric Juniper during story), Castelia City (Royal Unova on Thursday)
RageCandyBar – Castelia City (Royal Unova on Saturday), Prof Juniper at Desert Resort
Rare Candy –Castelia City (Royal Unova on Sunday), man in Anville town
Other:
Black Flute – Route 13 (Treasure Hunter)
Blue Flute – Route 13 (Treasure Hunter)
Red Flute – Route 13 (Treasure Hunter)
Shoal Salt – Route 13 (Treasure Hunter)
Shoal Shell – Route 13 (Treasure Hunter)
White Flute – Route 13 (Treasure Hunter)
Yellow Flute – Route 13 (Treasure Hunter)
Heart Sclae- Drifveil city (If you show a girl the move she requests)
http://www.gamesradar.com/f/pokemon-black-and-white-item-location-guide/a-20110310112141116005/p-3