I have a fair number of the older Bessey K body clamps with the wooden handle and they work fine. I do prefer the newer K body Revos as the new soft handles are much easier to tighten. I agree though that the clutch sees a bit fussier than the old version. I have gotten all mine from the box stores, most of them when they had sales, but they don't carry them here anymore.
I also have some Jet clamps and when they work right are great. Two out of my four started slipping a couple years after I bought them. It's weird, they tighten down really snug but when I check them later they are loose. I called Jet because of the lifetime warranty but they required me to send the clamp back on my own dime for them to look at it. But given they are 50" clamps, shipping was going to be more than half the price of a new ones.