Hello, I have gotten my correx from bunnings my local hardware store. Any hardware store will usually have correx, I'm not sure if they have bunnings in the USA but like I said just a hardware store...
I'm not sure on the grids, I never used them as before when I has my pigs inside Gizi was still small but soon after she learned how to jump over even 24 inches. So I moved them out and just didn't bother to get grids.