Please recommend your reformer towel/pad

I'm not tall, but every time we're on heavy springs my shoulders jam up against the reformer blocks. This happens even when I've scooted down a few inches as directed by the teacher. Looking for something to help me stay put (and yes, I wouldn't mind a barrier between me and the well-used headrest either).

Does anyone have a non-slip towel, pad, or other type of cover they can recommend?