There are aftermarket ball joints available to do the ball joint only. It would be wise to inspect the lower control arm bushings before doing the ball joint only or you will be doing the entire lower control arm including another new ball joint in a few months.
Just how loose is it? A very slight bit of looseness is not a problem. Years ago, ball joints were heavily oversold because the factory joints had a very small amount of play but were still in factory specs. I had someone try to sell me new ball joints on a six month old car back then.
