Here's a commercial circle jig. Seems simple enough. Now what if you want this thing -Right Now-? Well then you better have a Laser Cutter and some Acrylic.
Step 1 of the design comes from measuring out the dimensions of the existing router plate. What are those curved holes for? Who knows? But they look cool right?
Starting from a base circle of diameter 1/4 in (size of the router bit) we offset another circle at some whole number of mm to mark the smallest radius we can cut. Then we offset a whole bunch of other circles in 2mm increments. Then add some horizontal lines.
We want to place the center holes at intersections of the horizontal lines and circles. It took forever. And ever. That's a lot of holes.
Then you throw that on the laser cutter and BAM! New Circle jig. Well with some post processing. The laser cutter can't inset the screw holes for attaching this thing to the router. Those were cut with... A router. How about that