two thoughts:
does it have to be camlock? how about a simple screw-down device.. a gearbox could speed this up if you're bending alot of work and/or working with alot of thicknesses.
you could link two small gearboxes and have one handwheel close the entire brake down.
re: camlock -- camlocks aren't all necessarily positive lock designs.. that is, your cam doesn't have to directly contact your work. use a cam-follower type design and you can move the cam off (or further away) from the work. imagine a disk with a circular slot milled in it. put a pin through it, off center, and attach a simple handle/lever. then, turning the 'handle'
360degrees will swing your follower (riding in the milled slot) through the offset distance. the follower can be as simple as a dowel pin (ok a big dowel pin) on the top 'jaw' of your brake. play with positioning it before bolting it in to avoid the (not so sweet) "sweet spot"
-- the point where the cam can 'slip' and unlock.
hope some of that helped,
-tony