Hello friend, today you are lucky that there are cheap design solutions. I have two options to suggest you, the first is a single piece that you can order from anyone who makes 3D designs that you can print, just give them the measurements or take photos, or bring the speaker. He can do it for you quickly and you could replace the whole thing to leave them all the same, I mean, with the same style. Here you could replicate those of the original by replacing the fabric it has with a grid made of the same plastic as the 3D extruder, you could even put the JBL logo on it and in one corner your mini "SurfRock66" logo, how do you see yourself with that model? ..wouldn't that be cool? Then you can paint them with any spray and in the color you want, even metallic and give it your personal touch. The other is to ask for the same thing but without the grille, just a support that can be mounted on the second piece and that could be embedded or screwed to the first part of the ceiling. You should only glue the fabric inside (not just any will work, I warn you, some fabrics with a lot of cotton or closed mesh end up making the sound shine due to its absorption of waves) and then you stick the logo. It is a little more difficult but close to reality. Look for any 3D printing design workshop and you will surely be able to solve your problem. There are more ways (DIY) but obviously they depend on your manual ability and knowledge, and if you have asked for help it is because you are not sure that it will work out for you.