Can’t you bake it to a texture? You can use a texture to control the density parameter of the particle emission. Or do you want it to update as you edit the material? You might try making the particle’s material use coordinates from the emitter, and use the same texture setup (in a node group) to make the particle transparent.
This is kind of a hack, but it should help while you tweak the material, until you bake it. Note that this only seems to work with object coordinates.
You can get slightly more freedom with the From Instancer node option if you use a Particle Instance modifier, but that’s a lot slower when you have a lot of particles.