Another option, again pricier than the Pittsburgh clamps at HF: Dubuque aluminum bar clamps. They are the same idea as the Pittsburgh Clamps, but executed better. I’ve only had mine a short time, but am hopeful they will work well.
By the way, my next step with the pittsbugh clamps, if someone wants to try it, would be to replace the thin wooden piece that Paul glues or tapes on (to prevent marring) with one that is perhaps 1″ thick. I’d attach this block so that it rides against the bar, preventing the sloppy jaw from flopping over and digging into the bar, which is the source of my problems. It will probably be necessary to drill the moving clamp face to attach the block with a screw or two. Don’t forget to file off the old burs that have been dug out of the bar already, which like to catch the jaw and make it cam over again.