no real aftermarket support. the only ones that keep coming up when you search are some no name replacement control arms. not sure about the quality but never even heard of the various companies that sell them.
anyway, agree, find a used one. I actually had to put tack welds on my upper control arms when I put in new ball joints to hold them in. the threading on the ball joint and control arms is really not well planned. I have the socket tool but I have yet to be able to remove any old ball joints from any of the upper arms I've worked on, even with a high torque impact wrench. I just ended up pressing them out, thus the tack welds when I pressed in the new ball joints.
any 1972 thru 1993 upper arms will fit.