Couldn't you build something like this? Use some heavy wall tubing and maybe fill the bottom third of it with sand and the rest with rubber chunks from recycled tires. If you don't have a welder it wouldn't cost much to have a welding shop weld a flange on each end that you could bolt a thick plate to. Obviously the plate on the top you'd want to have a hole in the middle of it. Add a base to it and you're good to go.
http://www.actiontarget.com/store/cl...ring-trap.html