The screen is not designed to be user interchangeable (I’m certain about this) and as far as I recall the FA/FE/FM screens do not fit. Your best bet is a used EM with a good screen, a used part or that someone on eBay has a NOS screen. For example:
Nikon Fresnel Focusing Screen from a Nikon EM | eBay or
Nikon EM Focusing Screen Original Spare Part | eBay (no connection, just found through a search).
On any Nikon where the 3 series screens for the FM3a fit, I use them, but I am fairly sure that this is not the case for the EM. You might be able to modify one to fit, but again, I’m not sure.
I like the tiny Nikons although the FA/FE/FM cameras are more capable.