SusanC111:I got mine at the hospital. They are made by enfamil. They're supposed to be disposable, but I wash them and reuse them. I use them on the RTF formula, and they fit on medela bottles. I like them way better than medela nipples--no collapse. Maybe you can order them online?
heres what I have:
http://www.amazon.com/Enfamil-Slow-Flow-Nipple-12-Count/dp/B004TON9BK