I've created an account to ask this very same question. Absolutely loving this game so far, but after being almost softlocked trying to beat Groundon in expert mode without being able to go back and buy fresh items, I realised just how much I would enjoy the game having the inventory password.
I came looking for it in this thread: I am unsure whether this is one of the "mysterious three passwords" the creator has hinted is somewhere in the game that we need to search hints for, or if it simply does not exist. If anyone has access to it please do share. (Or if the creator would like these passwords to remain incredibly eluisive, please do send a message to me or Adrian!)