I don't know about you but I always have problems with the "Mirror Vertex Group" and "Mirror Vertex Group (topology)" tools. In fact, I never understood how they're working.
So I write this little script to copy the vertex group from one side to the other. It's not very complex and not very great but it works.
You can download it from https://github.com/LWH-21/blender-mirror-add-on Documentation is included.
Please let me know if you find bugs or have suggestions for enhancements.