Glenna Partridge Garden Design When I'm in San Francisco I go to Paxton Gate to find really cool pieces of coral and shells. Here's the link to their site and they are also on Houzz here if you need to contact them directly.
Joel Kelly Design These actually came from a shop on Magazine Street in New Orleans...if you're ever down that way, it makes for an excellent stroll with nearly a hundred shops and boutiques filled with extremely intersting and unique treasures.
A larger piece of coral can really hold its own on a case piece. If you want coral that stands proudly, search for a piece with a flat bottom. An acrylic base, a little super-strong glue and you're good to go!
http://www.paxtongate.com/searchresult.aspx?CategoryID=42
I hope this helps!
Glenna