I just talked with INCRA- in a few weeks they will be selling American made handscrew furniture clamps in 6" (used by Perry McDaniel in the I-BOX demos), 8", and 10" sizes.
I picked up 4 of those when they were last on sale. They're good for the price. I like the ones Woodcraft sells slightly better, but don't regret buying these on sale. The WC ones are slightly thicker and have a more substantail metal screw. But these work fine.