Unfortunately, Triumvirate cannot be crafted. Some unique and set items can be crafted in D3, but not this one, as it's official Battle.net page shows.
Therefore the only ways to get this item is by getting it to drop, or buying it on the auction house.
You can wear lots of magic find to improve your chances of finding uniques, but at this point we don't know the loot drop formulas to know where to farm for an item if you are looking for a specific drop: certain monsters in certain difficulties can drop items of different type and level, but we don't know what these rules are (yet).
So your best bet is to search for it regularly on the AH. You can ask friends to keep an eye out for it too, offer a bounty if anyone finds one, advertise in general chat, and so on. You can of course farm other rare and unique items to offer in trade, or to sell so you have the money to snatch up Triumvirate when it appears!