Thank you for your reply!
I am looking on UK ebay and the offer is pretty limited.
As I read, Kiev 88 screen has split image. I also checked Rick Olenson's screens and they seem to offer split image. Maybe I'll order one.
I intend to shoot most of the time with a tripod. When shooting handheld, the 35mm rule of thumb applies on medium format too? (minimum shutter speed=focal length of lens used)