Two versatile, adjustable router circle jigs that offer excellent precision, and do not require unscrewing the base plate. A rugged, low-cost design that is compact, easy to store, and sets up in seconds.
I am not offering plans, because this jig has to be adapted to each router model. However, the video contains all the critical dimensions and enough construction detail to guide a viewer who wants to build a similar jig.
I am not sponsored by DeWalt, Coca Cola, or any other products seen in my videos.

Sources for components:
The plunge router I used: https://amzn.to/2F47kGG

Ordinary steel rods are widely available in most hardware stores, and from many online sources. The zinc-plated variety resists rust better than the plain steel. Precision milled rods, such as those for CNC machines, are not required.

The threaded inserts I used are a zinc alloy made by E-Z Lok and available online. A package of 100 costs about $15. Many other suppliers offer similar products, and they are available in both metric and imperial sizes. Many hardware stores carry them.
Skate bearings measuring 22mm wide with an 8mm hub are available in many stores that supply skateboards and roller skates, as well as from more than 20 different suppliers online. They are typically about $1 per bearing. Cheap ones will work as well as premium versions for this use. However, the exact inner diameter of the hubs vary from brand to brand, so measure them with a caliper to match them to the threaded rod you are using.