We got to check out some of the new DeWALT trigger clamps.  They come in a variety of sizes and the larger ones have a spreader function.  A quick change button allows you to convert it in seconds.  These clamps are really no thrills but they get the job done and have a good solid grip.  They have grooves in the pads for bar stock.  They come in various sizes up to 50″, check DeWALT clamps via Amazon.com.