Ehh, I've found a Rosa Luxemburg collection at a Half-Price Books. My copy of Jon Lee Anderson's biography of Che Guevara came from a Barnes and Noble too. Anderson isn't really a leftist, but he does give a straightforward and sympathetic biography of Guevara, instead of the normal liberal demonizing.
Half-price doesn't count tho. They don't buy those, the people in the area sell those to them. Even then my halfprice has 5 "court of the red tsar"s for every Reminiscences of Lenin or Red Star Over China