* You can store all ID's in some sort of List object. Then when the player goes to buy an item, if they are an ironman, check if that item is contained in the list and then block them from buying.
* Second option would be to maybe update the GameItem container you use to have a canIronmanPurchase flag or something, this way you aren't looping at all but just doing a conditional check on the item itself. This however would most likely require you to flag every single item in your configs. If you could find a way to default set the flag to false for every item config then this would probably be the best as you could just go set flag = true for all the ones you want blocked.