What rotten luck - but it might be repairable if an optician can take the two screws(?) out and screw a new side on. If not, then carefully applied epoxy rosin might stick the end of the earpiece into the rightangle between the metal bar of the broken-off end and the screw, parallel to the broken off bar.

(I was an unpaid family carer for years, it's amazing what can be invisibly repaired and last for a long time afterward.)