Beattie (Intenscreen) makes a split-screen and I wish I was bringing you some good news but it is an awful thing to use. While the lens is unfocused it blocks the viewfinder too much to be useful. I bought one through bhphotovideo and after my complaint beattie accepted its return and were wonderful for the support they gave me but the screen is woeful. From bh they are non-returnable and its odd that no one on-line says anything about them ...even bad. I was lucky to be able to return it and made a fuss about it not being fit for purpose.
Beattie Intenscreen for Nikon F100 - Matte with Grid & Diagonal Split Image B&H# BEFSSIDGNF10
I use my F100 a lot and with zeiss lenses and for street so I am mostly using wides 21 28 35 and with film and also use 50 100 and 135mm.
I'm also fond of the standard F100 screen and its not so unlike the D700 and maybe a little better but not as bright and with the split prism of the FM3a.
ɹǝpun uʍop puɐl ǝɥʇ ɯoɹɟ
I've found using manual focus lenses (F5) with wide apertures makes it easier with the original screen. I use the rangefinder for rough focus and work from there.
I have a grid screen in one of my FM2's. It is a fresnel screen and I find it focuses perfectly OK with all lenses, particularly good with tele lenses.