I am not an expert. I think any RB prism will work on RZ or RZII . The prisms that have a battery built into the prism should work. The AEII prisms for the RZ67II are getting pretty cheap. I paid 1100 USD for mine, used in 2001. These prisms are nice but very heavy. Consider a simple "chimney" finder , weighs almost nothing and gives you a nice magnified view. These can be bought very cheap and are great.
The non-metering prism can be used with all RZ and RB according to documentation.
The chimney finder will not work on RZ II without modification.
See attachments.
There is an AE chimney finder built for the RZ that does not need modification. As mentioned all of the prisms work, I prefer the AE-II. The electronics for the meter do not add much weight. None of the RZ prisms have batteries internal to them, they use the camera's batteries for metering/etc.