Any rigger will stock the balls for the Antel Car US or foreign. Usually cost is about 50 cents per ball.
When replacing the balls you may look at the shackle as provided by Amel. The Amel unit has a welded bar on the shackle. Most have broken. All 
shackle manufacturers strongly that you do not side load the shackles.  My fix is a $37 US 6mm plate welded to the shackle.