The NRA has one or two, but not sure if it's over priced, I am a life member but that doesn't mean I blindly pay out what ever they ask. You could also check with Cheaper Than Dirt, and both Gander Mountain, and Bass Pro shop, although I think the last two may well make the NRA ones look cheap. Check down on the Accessories board at the bottom, we may have some idea posted there also.
Just for grins and giggles, I did a Bing search and came up with this site. Looks like decent prices at least for the IDPA/IPSC target stands, but they do appear to have Metal Pop ups I think
http://nevcotargets.com/catalog.html If you want something that looks like critters then maybe these guys:
http://www.metaltargets.com/SpecialtyTargets.htm I got a few hits, but hopefully you may get someone here that can narrow down what you want/need, much better than this.