Look for metal fabricators in your area.
I live in a smaller town and walked into a local guy's shop and told him what I needed. Two days later I had this:
He used cheap 1/2" plate. It dimples badly, but...replacements, up to 10" square are $8 and last a long time.
I used coat hangers to hang plates because I get bunches of them when I have my suits dry-cleaned and are easily fixed in the field should I hit one. Lengths of chain look way more cool, but take more time and money to acquire and fix. Nothing wrong with chain, but I seem to get good mileage out of hangers.