They don't supply them. I asked if they had restrictions and they said anything was fine. The plastic ones feel gross to me, but I hate to spend so much on something that will be used such a short period of time. I didn't think about a king sized pillow case fitting on there. That's a great idea.
Mama to Henry (01.07), Catherine (09.11), Audrey (04.14), Clare (09.15) and our newest addition, coming July 2017!