I think most of the descriptions do list the width of the hilts, usually under the "Specifications" section. Usually as X" wide or width.
For example, the Sentinel V4 lists a 1.45" width. The Lost Gray lists 1.6" width. The Menace lists 1.5" width. Aeon V4 lists 1.45" width. Savior lists 1.5" width, etc. I didn't see a width on the Fallen, but most do seem to specify a width.
This old topic seems to list some with a 1.25" width, which they said was, at the time at least, the thinnest ones they offered:
http://www.saberforum.com/index.php?PHPSESSID=4oadntiv6p1eqndt38lb746os7&topic=4779.0Multiple people in multiple places I've read have said that some of the V2s are the thinnest ones, but that was at least a few years old based on the dates listed.