Clutch Problem

So i was driving the other night, and all of a sudden my clutch started going straight to the floor, and i couldnt get it into gear. i pulled over and looked at the pedal and the white plunger? had broken in half (see picture). Does anyone know what the technical name for the part is? Can i get just that part, or do i have to get a new master cylinder? any help would be greatly appreciated.