I'm assuming it's a Skunk2 kit or something like it? Have you contacted the manufacturer to see if they either supply new ball joints (which I'm sure they would as it's a part that wears out) or if a new ball joint from Discount Auto Parts would work? I have yet to replace these on my camber kit so I haven't found this out for myself but I did notice during my last rebuild that I tore one of the boots and was going to look into replacing it soon.