I've used these black grommets since I started buying dolls for the issue where her heads screws on but tightens up backwards or sideways. These allow for a lot of play and have always worked. Recently, I noticed some discoloration on the TPE at the top of my large torso's neck and know this is the culprit.
I looked into felt washers but most are small and for musical instruments or lighting rigs. I had picked up this felt pack from The Dollar Tree a while back and found it while looking for something else today. Of course, these are far from perfect circles, but they don't have to be. They'll be hidden by my girls' heads and it should allow me to continue using the rubber washer as it the issue with TPE contact is only at the neck.
Thought you guys might like to give this a shot. It's been a cheap and lasting solution with the grommet and for $1.00, I got 8 total washers.