ORIGINAL: Mike from Texas

Make your own. Go to Home Depot and get some of the foam insulation that is used on houses. Layer them on top of one another andput 2x4s top and bottom with all thread rod between to tighten them down and compress it. Same principal as the block type targets. If youu don't need on 4x8', just cut the sheets in 1/2 and have a 4x4 target. As the lasyer start to wear and it gets loose, just tighten up the all thread rod.