The Gadgetron Personal Delivery Assistant, or Gadgetron PDA, was acquired from "Steve McQwark" on planet Oltanis. It could be used to purchase ammo anywhere in the game with an added shipping price. In Up Your Arsenal it was available at Qwark's hideout in the Thrann Asteroid Belt.
In Size Matters, Ratchet could purchase it at a Gadgetron Vendor.
In Secret Agent Clank it was called as the Agency PDA because in the game it was the Agency's not Gadgetron's gadget.