Reading particle data from another system in Niagara?

Hello!
How can I reference emitter inside of one Niagara system, to another emitter inside of another Niagara system?
I need to use “Spawn particles from other emitter”, but this emitter is outside of the current Niagara system.

I saw Particle Attribute Reader that exposes emitter on BP level, but I cannot put in the system that contains the emitter.

Thanks for any help guys.