Need Help security signs

So, I need a little extensive help on security signs. I have a security company for a neighbor who wants to purchase a large quantity of signs for me. He wants them for the customers' yard signs. I THINK the substrate I found is aluminum 4 ft x 10 ft with .040 mil. Then I was going to print on the vinyl and then install on the aluminum. The corners on the aluminum need to be rounded. How can I do this (cheaply, effectively). It's 250 signs for 1000 corners. Can I take them someplace and have them cut? Or is it really easier for me to try to find the aluminum substrate already cut? What about the stakes? It doesnt look like I can purchase any of these items from my supplier. Except maybe the corner cutter? But I'm at a loss as to how to cut the corners (literally! ha)

 

Apparently I have found a place that will cut 4ftx10ft aluminum to 10 inch x 8 inch and round corners.