How to export Realtime Shadows to PNG

I have a very simple scene with a Camera and a car. I am currently using realtime shadows with max settings on URP. Since I am making this game for mobiles, it would be inefficient if I continue to use realtime shadows. So, I came across blob shadows and they are awesome! But how do I export that realtime shadow to a PNG file such that I can use that inside of Blob Shadow Projector?

Here is the camera and the car with shadows :-