Search the following locations to find stamps for Niko:
Desert Realm Sand Sanctuary - Beat Sand Temple to unlock Sand Lokomo's sidequest, then finish it. Get a Cucco, and fly to the island in the southeast corner of the area. Sand Temple - On the west side of the sand river on the second floor; Sand Wand required. Spirit Tower - At the very top of the tower.
Fire Realm Fire Sanctuary - Light the torches to unlock the bridges, north part of the area; Boomerang required. Fire Temple - In the room with four eyes next to each other, shoot the hidden switch in the southwest corner with an arrow; Bow required. Goron Village - Northwest corner of the area west of Goron village; instead of crossing the bridge that you activate, keep going north, and use the Snake Rope to get across.
Forest Realm Aboda Village - Next to the train station. Forest Sanctuary - North part of the map, near some stairs. Forest Temple - First floor, in the poison gas room; Leaf Vacuum required. Hyrule Castle - Northwest corner of town; Bombs required. Trading Post - Northwest corner inside the cave; Bomb required. Withtleton - Near the entrance of the north field.
Ocean Realm Papuchia village - Southwest corner of the islands south of the village; Snake Rope and Bird Song required. Pirate Hideout - Center of the map, on the hill; Snake Rope and Bird Song required, and Force Gem required to unlock Pirate Hideout. Ocean Sanctuary - On top of the entrance to where the Lokomo is found; Snake Rope and Bird Song required. Ocean Temple - Bomb the north walls on the second floor, inside the opened room; Snake Rope and Bombs required.
Snow Realm Anouki Village - Northeast corner. Snow Sanctuary - East area of the map, on a small hill. Snow Temple - Northeast corner of the room full of water and five torches; Boomerang required. Wellspring Station - Passing the lake using the ice torch; Boomerang required.