I'd check with petra cycles before ordering - the pic in that second link is of the right part, but the part number is not. part number for the concave washers ("lever boss cover" is the shimano name for it) is Y-643 38101, but the part number for the flat type ("Lever boss cover for light alloy frame") is Y-643 43000. Here's a link to the official shimano spec sheet. The exact same part numbers are also used in dura ace (and all other) levers).
http://techdocs.shimano.com/media/techd ... 609217.pdf
Andy
http://techdocs.shimano.com/media/techd ... 609217.pdf
Andy