The bike shop threw away ferrules for both levers.
I wasn't able to get a good measurement so I took this from an eBay auction that mentions ferrules for my handles.
"The cable opening at the top of each brake lever (and underneath the rubber hood) measures about 10 mm at it's widest point...a diagonal measurement...and about 8 mm at it's narrowest point...to form an opening that has rounded corners, but resembles a square in shape (and with this particular model only...this cable opening tapers down to about 7 mm in diameter...to form a circle...further down in the brake lever)."
[IMG]file:///Users/kylewrobel/Library/Caches/TemporaryItems/moz-screenshot.jpg[/IMG]And this is an image they've included. Only problem with this auction is that they want $70 for a new-old stock.