The option from XuanLens offers a 28mm view, but also has markers to indicate what a 35mm and ... the generic viewfinder may be a bit of a risk. But the temptation of an optical viewfinder with ...

With a 35mm equivalent zoom range from 35 to 210mm ... the one fly in the ointment being an optical viewfinder that's excessively tight, showing only about 77% of the final frame area.