Pölter noises on the rear axle

Hi V8ler,
I have looked what the polter noises are on my rear axle and have recognized that the ball heads on the wheel side (i.e. the outer ones) of the fall adjustment have been knocked out on both sides.
Does anyone know what they cost? I didn't even see if you could change the ball heads or do you need the whole handlebar?

Thank you Björn