Mamiya USA no longer has the parts to convert the older finders for AE operation. A newer model exists that will work on the RZ Pro II and probably on the RZ Pro II D.
I recently bought two of the newer finders on Ebay.
Call Mamiya USA Service Dept. maybe they have a demo kicking around the shop.
J-Knight - Thanks for the info!! Glad to hear there could be a version kicking around that I could use. Sorry to bother but could I ask you to post a pic of the newer finder so I can search on E-Bay and make sure its what I need?