Try http://tesnexus.com/downloads/file.php?id=24473. I haven't used it myself but it says it makes all vanilla helms and hoods protect you from sun damage. Personally, I think an outfit would need 100% skin coverage to prevent sun damage, but it depends on how sensitive you see vampires being to sunlight. There's one end of the spectrum where they run through the sunlight with a little smoke coming off 'em, and then there's the other end where a single ray of sunlight on their skin burns the skin right off and then they burst into flame. Don't even get me started on the sparkly diamond skin thing.
Anyway, there are other options as well such as http://tesnexus.com/downloads/file.php?id=24405 (uses a ring instead of helms/hoods), and then several that do away with sun damage altogether. Just go to nexus and do a search for the word "sun" - it finds numerous results, including these.