Found this site http://www.bfmarineinc.com/ and bought a 4 inch deckplate for 13 bucks. I bought the part number 111133009
Click on anything in the Products on the left side, then use the search window in the page that opens. Put in deckplates (one word).
Pricing for shipping is a tad high, almost 8 bucks for UPS ground and I'm only half a state away from them (they're in Miami).
Huh...seems just clicking on the part number I gave links you right to it.