The bargains and prospects mechanic is very promising. I usually try to fulfill the prospects fully to receive the additional bonus. The most effective way of doing this is via bargains. This sometimes requires accumulating the target items over time in the bank.
As a result, I often find myself unable to decide how many items I should buy from a bargain. I can see that I need X items to fulfill the prospect in the Locomotive view. I can see that I can buy Y items in the bargain. But I don’t remember how many target items I have in the bank.
I would suggest to allow the player to view the bank account at any time (without the ability to withdraw items). It will make it much simpler to manage your prospects progress. It also makes sense lore-wise – the captain probably has this information in their ledger.