Even if a store carries it when available, you often will not find it. Most retailers simply can't keep it on the shelf. Check back often or find out when a new delivery is expected.
You can sometimes find it at Cosentinos at Bascom Union. I also hear Maplewood Liquours near the same intersection carries it.
Wine Affairs near the Town Theatre has it on tap. They also have lots of other craft beer. Check out their beer menu on their site: