You can earn these in Rob an Electronics store, and Arrange a Drug Shipment for the Mafiya in Moscow. They are Special Loot, have no attack or defense, and 333 are needed in NY. 412 are needed in Cuban and New York Missions.
They are also required in Moscow when selecting Mafiya in Episode 4 (Avtoritet). To gain the Mafiya loot 'Orel Armored Helicopter' it is better to select Mafiya on Level 1 when mastery percentage is higher. For example in Level 2 Mastery is 4% meaning you will need 25 Untraceable cell phones to complete the level.