How does the Assassin's Creed Brotherhood buy climbing gloves? Please give me a sleeve sword. Tell me more specifically.

In the fourth chapter of the main plot, you meet a little boy crying by the river. After helping him save his mother, when you return to the bridge of the assassin base, you will hear Da Vinci calling you. At this time, you can buy a pair of cuff swords, climbing gloves and poisonous darts, and you can only buy one at a time. Then look for the "L" sign on the map, and you can ask him to buy the rest.