I recently stopped by Bad Dog Burls in Belcherville, Mass and visited with the owner Rob, high quality stuff..  If you are looking for high quality burls, especially Australian species this is the place.  I picked up some pieces for some segmented bowls that I am working on.  I have attached a photo of some of the wood I purchased.  Red Mallee, Gaint Mallee, black ash burl board, to name a few and a banksia pod.

You can see what they have at:

http://www.burlsource.com/