Finding all of the rare trade objects in Assassin's Creed: Brotherhood can be infuriating, what with random item drops and quests to juggle. Watch this video for a guide to farming trade objects by killing bandits along a particular route.
From the Creator:
Bandits drop a lot of rare quest items. A lot. Two farming runs with no editing - one take.
Here's my Tradable Item farming route. Not sure if its been discovered already, but I'm documenting it anyway.
Wait until nightfall!
Travel to Palazzo Laterano (you might be able to travel closer - but I'm superstitious)
I walk to the location near the bottom of the map because of superstition mainly :P
Walk along the path until you hit a crossroad with a small hill with trees on it. Bandits attack from around the hill. If they don't attack straight away, walk a couple of times around it. Kill them, loot them, repeat! Works every time (at night) for me. Sometimes I have to go to dash and restart though, so almost every time. :)
Items I commonly get:
Vlad the Impaler Coins
Cardinal's Purple Dye
And Shrunken Head (apparently. if you do my route, let me know if you get a Shrunken head!)
Right, so I've been trying my bloody hardest to get do my last shop quest (Exotica), all I'm missing is a 'Shrunken Head'. After going to every treasure chest in Rome I'm still missing one, so I tried something else. I heard rumors that Bandits that "randomly" attack you have a small percentage of dropping Shrunken Heads, so after wandering around aimlessly I discovered bandit attacks aren't random and I found a way to make them spawn almost every time. Here's my farming route which has been giving me incredible results.
Also, mail carriers frequently run along the road. I was able to get Aconite from one of them.