Where do you find an Untraceable Cell Phone?

To find an untraceable cell phone, do the "Rob an Electronics Store" job at the Enforcer tier in New York. there you will have a chance to loot randomly either of these 3 items: untraceable cell phone, concealable camera and computer set-up.

You can also find an untraceable cell phone in Moscow, Episode 1, Baklany. Do the "Arrange a Drug Shipment for the Mafiya" job. You will have a chance to loot only the untraceable cell phone.