I made some of these when I was breastfeeding and decided to make some for my sister too, she is due any time now.
I made these a little larger than the ones you can buy and I used rubber sheeting in the middle of 2 pieces of absorbant flannel so that the occasional mishap won't ruin your outfit. You will need 2 pieces of flannel, 1 piece of rubber sheeting(If you wish) or you can use more pieces of flannel if you don't want to use the rubber sheeting. Cut out the desired size circles (I made the rubber sheeting about 1/4 inch smaller in diameter so it wouldn't show outside the stitching. Sandwich together your pieces