Good luck in your search, the ETRSi standard screen only came with a matte center spot; the 135 optional screen had split image finder.
The earlier ETRS had a split center surrounded by a matte ring for the standard screen.
The Beattie and other 'brighter' aftermarket screens all affected metering viewfinders, forcing you to adjust the ISO value to compensate the meter.
Ian B. Photo in the UK has a Bronica ETRS (diagonal) Split Image / Microprism focusing screen. I bought some stuff from Ian in the past (especially for my Bronica) - he is a reliable.
Those used (Bronica) focusing screens all have some marks because of the soft surface.
+1 for Ian B. He has a lot of Bronica items at decent prices, I've bought a lens and several parts/accessories from him in the last year or so.
The only item I had an issue with was an SQ-A speedgrip that was damaged and badly repaired; a big crack inside it was covered in glue so it wasn't apparent until it broke over a month after I bought it. Ian replaced it immediately and covered the return postage