Try custom builders, also. Slate in larger pieces has lots of uses: counter tops, bathroom vanity tops, fireplace hearths and surrounds, etc. It isn't cheap, either. Seven or eight years ago in San Diego, counter tops were running upwards of $30 per square foot installed. You wouldn't get that much for it because they'd have to cut it to size, polish it, etc, but you might want to try shopping around for a good price.
I'm thankful I don't have it - my wife would have me re-topping the stupid breakfast bar and I hate that kind of work.