I have a couple like the one in the Cabela's link. It works great and keeps my bow/cam off of the ground.....unlike the one Rick posted about. I just don't like the idea of the cam/string being in the dirt.
Also, you can go to Home Depot, get a long piece of round aluminum and make your own. You just need a bench vise and some large pliers. I made one for my son and then dipped the "bow holder" end of it in a rubber dip a couple of times to add thickness of the rubber.
Greg