Are there any stores that still sell used PS1 and N64 video games?
There are little niche stores that still buy old systems and games from people and re-sell them, but they can be hard to find. Try looking in the phonebook or at an online phonebook for video game stores that you haven’t heard of. Usually the places that buy these older games are non-franchise establishments (the opposite of Gamestop and EBgames which are nationwide). I doubt the Salvation Army would have any games.