If you sharpen your own handsaws or backsaws, the Gramercy Tools 14″ Saw Vise, seen on Ron Hock’s The Sharpening Blog, might just be the clamp you’re looking for. Its ¼” thick machined steel jaws are set at 45° to the saw, providing clearance for your files and allowing you to slope the gullets. The rotating clamping cam has lots of travel and provides plenty of pressure at the jaws. It’s designed to be bolted to a bench for more rigidity and less flex.
The Tools for Working Wood site has some interesting notes on how the design process went for this saw vise.
The vise’s pre-production price is $98.95 (shipment “sometime in October”).
14″ Saw Vise [Manufacturer’s Site]