I'm not sure about inverted exactly, but my sister and I had to use the nipple shield to help "pop them out", LOL. :) Here is a link: http://www.toysrus.com/product/index.jsp?productId=2793358.
Some of the reviewers mentioned they had inverted nipples and it worked for them - so hopefully it can help you out. :)
I don't have inverted nipples but ever since I have been pumping I notice my nipple are not what you would call longer or harder but it pulls them out and more and it also helps my son to latch on better