If you get the Twins magazine, there are several advertisements in there for the kits another person already mentioned. You also could go to the NOMOTC (www.nomotc.org)(National Organization for Mother's of Twins Club) for links. These are both great resources for a mother of twins anyway. If they were in seperate sacs, they most likely are fraternal, but it is possible that they could be identical. Identicals can be in seperate sacs. I had the same issue as you. When I first found out I was pregnant with twins, they were in seperate sacs, but the dr. said the membrane between them was so thin, he felt they would be identical. When they were born, I was able to tell they weren't by eye color. Both have blue eyes, but one has light blue and the other dark blue. And now they are 5 years old and there are other differences as well.
If you are interested in a Mother's of Multiples club, AMAMOM is a wonderful club. It meets in McKinney and serves the Allen McKinney and surrounding area. We have lots of fun. Our website is www.amamom.org. We are having a huge garage sale next month.