Yes, there is a 35mm finder - you are looking at it, and it was produced specifically for the Sony RX1 35mm fixed lens camera.
Zeiss never (near as I can tell) produced a 35mm finder for the Zeiss Ikon line, which is logical. They produced finders for wider lenses that the Zeiss Ikon rangefinder camera did not have built in frame lines for. The camera of course has 35mm framelines.
At this point the only source of this finder is Sony and presumably because of this you can expect to pay more for it.
They'll be available starting early to mid December and will cost a whopping $599, far more than the Zeiss Ikon optical finders can be purchased new or used today.