Transmissive Particles in URP

I'm trying to make a light shaft effect at night using the Unity Particle System. I've set up all setting except my own particle sprite, but I've run into a problem that I don't think I can solve without an in depth knowledge of HLSL.

My particles use the urp/simple lit shader although I've tried lit as well, and all particles are lit towards the normal (see my first image) which looks excellent and is exactly what I'm looking for. However the backfaces are unlit. I'm aware this isn't a bug as with opaque lighting you always make normals away from the light dark, but I want these backfaces to be transmissive so I can see the light fog from below (see second image where all the particles are backfaced and the scene looks rubbish). I imagine the technical fix is to copy the shader but make the backfaces render with the same normals as the front faces. How can I do this?

 

You needs the translucent shader...
Search about translucent material tutorial for shader graph