The pillar covers on mine don't appear to have the foam backing - only fabric. Of course, it's possible the foam has all disintegrated over time.
If it is just fabric, you may be able to remove the piece, peel off the fabric and use a spray adhesive on the plastic part. Then carefully roll the fabric back on.
I would try an upholstery shop first, though, as MoistCabbage suggested. It may not be that expensive to have them do it with new material.