If its so important, ask if they would be willing to put down a rug or carpet (the expense either split between you or even if you need to cover the cost alone) in the whole apartment or at least in the room on top of yours. As far as the earplugs and not hearing the alarm clock, I think they sell something that shakes instead of making noise, maybe something like that would work…? Is it as bad in the summer (with air conditioning)? If that works, maybe a sound machine would help. It might mean investing a few dollars, but its probably worth it to maintain Shalom.
Hatzlacha!