go to local welding shops. if you stay with soft point bullets you can get away with ar 400 plate for rifles or ar 200 for handguns
That's what I'd suggest, also where I get all of my AR500 plates. I cut them out myself and build my own targets though:
Weld shops, like mine, will have surplus/remnant plate left over from jobs. They would probably be happy to cut you out some plates, for quite a bit less money than what you will find them at the store..