Lee Valley, a canadian company has an amazing assortment of sharpening supplies(Stones, pastes, Strops, water baths, dvds, books, etc.)
Here is some of their Japanese stones which work on the hardest steels.
http://www.leevalley.com/en/wood/page.aspx?p=67089&cat=1,43072,67175
And their broader sharpening asst.
http://www.leevalley.com/en/wood/page.aspx?cat=1&p=43072
Cheers,
Mark