and if I hadn't bought those, they would have provided some as well. I only know of Pampers preemie xs dipes but don't know where to get in bulk. They used Similac Human Milk Fortifier but it sure is expensive as far as I can tell. Often when little ones come home their breast milk is supplemented with plain formula to add 2-4 calories per oz and it sure is cheaper though I'd be leery of using a can of powder in the NICU since it can grow dangerous bacteria quickly.
One thing I really liked using - my kids lived in Swaddleme's as soon as they could wear clothes. I liked giving them a slightly more wombish experience and the swaddler makes a "uterine wall" to kick against. I wish I had more help to give.