Try calling your local steel center or steel recyclers and ask about expended metal "drops". When another customer has them cut a full sheet, but doesn't buy a full sheet, they pass most of the expense to him.... and if the drops of expando are large enough they set them in a separate bin for small projects like yours. A steel center will have a bigger selection than a big box store. I believe my expando is #9 flat. The diamond is about 3/4".
They should let you snoop through the bin and pick the pieces you want. Expando comes in two profiles, flat and raised. Raised is more rigid and works for cooking grates, flat will roll easier. just make sure and pay attention to the direction of the diamonds when you select your pieces.
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