The corners broke off?
Cheap fast and simple cure, get four barrel washers (large washer with small hole) or cut four triangles out of black/white plexi to use as washers, and just put them on top of the pieces, screw/bolt it back in.
If you want to replace it, after you use the masking tape, sharpie, and digicam, take the old panel to a bowling trophy shop or a plexi shop, and they can make up a copy for you. (The trophy shop can engrave labels, the plexi shop probably has other virtues)
Or...Check out CNC Machine Shop | Custom Waterjet, Plasma, Laser Cutting | eMachineShop.com where you can download simple CAD/CAM software for free. Make up your own custom panel, on your computer, and they'll fabricate it and send it back to you. Wood, metal, plastic...one heck of a way to do a custom job.
Of course the washers will get you back sailing faster.