A friend of mine is looking for pictures to put in a book she is publishing about the Attica Prison Riot. The problem is that all the pictures that she can find online are owned by the Attica Prison and they want $350/picture. The riot went on for days, it was big national news, there are other photographs out there - but where?

New York state has actively suppressed access to these materials for decades and the New York historical society pretends that the event never took place.

So... Where would I be able to find unowned pictures? Are there any good historical websites, resources, etc.?