Front Suspension Control Arm problems of the 2007 Buick Lucerne

My car was not responding as it normally was and I took it into my mechanic. He put it up on the lift and discovered that both lower control arms were very worn and needed to be replaced immediately. It took him several days to find the left control arm. Her went on line and could not find any dealer that had the item in stock and was told that it was no longer available. He was told that gm had stopped making the part. He found that part at a parts store for about $70 more than the one part he was able to get at a dealer. The sad part was the part he found at the parts store was notably of a stronger metal and better construction that the original gm part.