Well, why drop the list at the end of the round? Just build and edit it as things are processed.

You may even want to try going with having a list/array of the types of resources your AI can use, and then having that list point to different kinds of structures to better sort out where the actual resources are. (Such as a quad tree or similar.) This way your AI actors can not only have quick and easy access to what resources are available, but the general location.

You could also sort some resources with a more complex data structure that will keep two lists, a primary and secondary source. Bakeries will be the primary source for most AI to buy bread from, and they will usually seek a baker first to buy bread from, rather than seeing if "random-dude-on-street-22" has any bread to sell.