There are several brands like AquaStik Underwater Epoxy that you can find at any LFS. Home Improvement stores sell similar products that I have used as well but do not recall the brand name.
Mark
What reference books and/or web sites do you use to help identify coral?
For books, I've used
Aquarium Corals by Eric Borneman
Corals, A quick Reference Guide by Julian Sprung.
On the web, I really like http://coralidea.com/
Mark