I should also mention the wheel covers have clips that grasp the outside of the rim, not the inside like many I have had in the past. What happens when a wheel cover gets old or damaged is that when a certain clip is on the bottom as the wheel rotates, the deformation from the tire moves the cover and/or clip, causing noise.
Here are similar aftermarket wheel covers I got, which I actually like the appearance of a little better than stock. The stock ones look a little flatter and these look a little curvier like the original steel wheel shape. A set of 4 is less than what 1 replacement Subaru stock one is. They are holding up well so far, although I usually remove them and reinstall myself when I go to get wheels rotated/balanced or alignment done. I don't trust even better shops to not get in a hurry and yank them off or try to slam them back on.