I just actually though of this as well... And when I clicked on the original post I see that I didn't read it well enough in the first place and didn't catch that you said NOT top and bottom, but only side to side.

And this does make it sound like the idler arm bushing because it's only happening on one side. My 142 was doing this for quite a long time until I got the bushing replaced... It isn't too hard to replace yourself if you have another car to drive and a local machine shop that's willing to push the bushing out for you. They shouldn't charge you more than $20 considering it'll only take about 5 minutes max for them.