HELP: Render Niagara to Render Target - Window Raindrops Effect

Hey guys!

I have a niagara emitter that spawns particles with a raindrop mask texture on a plane, nothing fancy. I also don’t need any fluid simulation stuff. I only use niagara to randomly place and fade out the particles on the plane and thats it.

My problem now is that I want to access the particles inside of my window material. For that to work, I need to render the particles to a render target that I can sample in my material.
And I know that I can somehow use Grid2D to write information to a render target, but I cant wrap my head around how exactly to approach this.
I dont want position gradients or anything like that, just the raw color information of my raindrop mask texture scattered over the plane, as if I would capture the particle system with a scene capture 2D in my scene (which I definitely want to avoid).

If anyone knows how to do this or can hint me in the right direction, that would be highly appreciated.
Thanks in advance!

EDIT: Before anyone asks, unfortunately I can’t simply use a flip book of a baked simulation, because I need the effect to be completely dynamic, since I want to be able to interact with the particles at runtime.