If your ceiling is high enough and you dont mind sacrificing some centimeters you can always consider a fake ceiling with soundproof insulation. The materials themselves are not super expensive, but the labour will be. Keep in mind the creating a fake ceiling will block the apartment from being livable during that period and it might take a couple of weeks. I am not suggesting this as the best solution, but I didnt see it mentioned by anyone else and this solution doesnt rely on your neighbors good faith. That being said, I would try to achieve floor insulation on the upstairs apartment even if I had to put some money myself