I've got foam from Walmart's craft section and it does a pretty good job, comes in 2mm, 3mm and different colors. If I may add if your going to use foam I would get the same color as the thread your going to sew if at all possible and a heat gun, the heat gun is for heating the small foam pc's sticking out...I know I did not explain the heat gun part just right but I'm someone else will help on that.
darryl