Okay, I just got my Platinum Game Guide, and I'm currently flipping through it.
Note that all of these items require the Pastoria City Gym Badge, which allows you to use Surf outside of battle.
Route 219, 220, and 221: Max Repel, Splash Plate, Carbos, Protien, Ultra Ball, Leppa Berry, Pecha Berry, Mago Berry, Hondew Berry, TM81 X-Scissor, Pure Incense.
Route 204, and Ravaged Path: HP Up, Sea Incense, Luck Incense, TM03 Water Pulse.
Floaroma Meadow: Leaf Stone, Ultra Ball, Miracle Seed, Rare Candy.
Route 205, and Fuego Ironworks: Sitrus Berry, Wepear Berrys(4), Kelpsy Berry, Calcium, Star Piece, Red Shard, Blue Shard, Yellow Shard, Green Shard, Fire Stone, Rock Incense, TM35 Flamethrower.
Valley Windworks: Electirizer, TM24 Thunderbolt.
Route 209: TM19 Giga Drain.
Okay, I gotta go to bed in a few hours, tell me if you want me to finish this tomorrow, because the full list is pretty long.