Note: This trick requires two gamertags and two controllers. If you only have one gamertag, create a second temporary gamer profile to perform this glitch. First, sign in with both gamertags. Start any chapter. Clear both players inventory slots. Have Chris give Sheva the item(s). Then, have player one quit, and save both profiles. Resume the game, and have Sheva give the item(s) back to Chris. Quit the game again, but only save player one's profile, and not player two's profile. Both gamertags should now have the same item(s). You can repeat this as many times as desired.

Start any chapter, and invite another player. Once the other player has joined, have them equip their inventory with the desired items. Then, have the player leave the game. All those items will still be with the player who just left and also with your AI partner. Transfer all the items from your AI partner to your inventory, then send the player an invite again. Repeat this as many times as desired.