deerkillindad21, I'd start by asking around any welding shops in your area. They should know where to buy steel stock. But they probably won't have the super-hard 500 Brinell stuff that MGM uses.
jmt1271, I have one of the
MGM Auto Poppers and it works great for the pistols. Haven't tried it with the .223 yet, but the web site says it'll last a long time if you don't get too close. The only complaint I might have with it is that it comes back up so quickly I sometimes miss the reaction behind the muzzle during recoil, especially with the .357 mag. Ordered directly from them and it came the day they said it would. I just looked and the prices went up since I got mine.
The
Loli-Popper and
Flash targets look interesting too, but kind of expensive. I think the Flash target was used at some SOF matches.