Binoculars can be found in many locations in Harran, all on tall buildings or other structures such as radio towers. One of these locations is in the Safe Zone radio tower near the East Highway Tower and bridge and is located on a crate near the sleeping area.
The poisonous weeds are called Wolfsbane and can be found along the drainage channel south of the safe tower. You will find three leaf icons indicating the location. When you reach the area, look east of the east leaf symbol and walk west past the drainage area.
Syringes and pain relievers for patches and medications can be found in medical containers around the world. However, make sure the dressings and medications match the search you are following or they will not show up. This video shows the games from the Xbox One version of Dying Light.
Lighter Gas (Mission) Lighter Gas is a side mission in Dying Light. You can find lighter liquids all over the map, especially in cupboards. As you follow your search, the lighter gas will appear more frequently.
Bandages and Medicine is a side quest in Dying Light. Available after graduation. To complete this side mission you will have to search for 3 pharmacies in the slums. The first is just around the corner south of the tower, next to Dr.
Lavender plants (herbs) are found in the eastern part of the slum, on and around some rocky islands outside the safe area of the ship. Some are in the bushes, so using your survival instincts can be invaluable in your quest.
As all of these items are medical devices, you can go to one of the slum pharmacies. One of the pharmacies is located to the west of the tower area, as seen in the first large image below. Another pharmacy is located to the northeast of the tower area, as shown in the second large image below.