My sympathies, MBE.
While you might find it at a junkyard, you'd still have to get a ball joint, typically they're ruined by pulling them out. You'd also have to get new bushings. If it was cheap enough that might be okay in the long run, the ball joints are pretty inexpensive even at retail (should be around $30) and the bushing set for one arm should be about the same price. The only other concern would be whether it's a weakness in the original design, then maybe a new one would be better.
If the place will let you supply the part, autohausaz.com sells it new with the ball joint and bushings already installed for $218, free shipping in the US.
Were it me, I'd have to basically be getting the used one free for the time and trouble of ordering the ball joint and bushings and then paying the shop to install those as well as the assembled arm.
Last thought: if you're somewhat handy, have a decent set of tools and a spring compressor, you can do it yourself.
Anyway, good luck and enjoy the ride,
Greg