I could be wrong but am pretty sure that Brazilian rosewood was an over harvest species and is now on not allowed to be imported to the us. sorta like Cuban cigars. you can't buy them here but any other country they are fair game.
i just saw some at wood crafters, boards up to 36" for lams and riser size blocks for between 10 and 30 dollars depending on dimensions
Shouldn't be too hard to come by. My best friends father has a few pieces, and he didn't have any trouble getting it. I think East Indian Rosewood is a bit harder to get. Both have quite limited harvest, but a "small" piece for a riser (for example), should not be a problem, as far as I know.