Instructions
Complete the game and wait for the ending credits to finish. Save the game when asked if you want to do so.
Go to the main menu. Load the game file that contains the completed game save data. A new game will begin.
Play through the first area of the game until you come to the Red Zone and meet the Mk. II robot. After this event, all previously owned weapons, ammunition, Drebin points and items are placed in your inventory.