When we built our race car hauler, we went to an aluminum supply place that sells to trailer and undustrial manufacturers. They sold us sheets of 4' x 8' that was 1/8" thick tread plate for about $120.00 The thinner the sheet, the cheaper the price. Don't know about polished or anodized. Most any large metal distribution place can get it. Also, race car trailer manufacturers will have some in stock.
One thing to remember, most all treadplate has a thin coat of oil to protect it during the shipping process, so this must be COMPLETELY cleaned before installation.
We used windshied ureathane glue, and never had one bit of trouble, but I'm really not sure if you would want to do that to fiberglass or not.

If this works I will dlete other if not I will try and delete both

Powerplay Racing's 33' Sportdeck Twin 640hp

engine compartment almost done