If you live in a university town, find out which dorms the international students live in, and locate the nearest trash bins. At the end of spring semester, during finals week, check in and around those bins daily.
The graduating international students who are returning to their home countries frequently discard things that they bought locally, as it may be too expensive to ship larger items in either direction. Those who will be returning in the fall might put their dorm stuff into storage, or they might just toss it, and re-buy if/when they return.
The cheaper it is to ship, store, or sell, the lower the quality of the items discarded. That's why you focus on those who will be flying home.