Zacuto has an updated kit to allow the Zacuto Z-Finders to work with the new Panasonic GH3 cameras. If you already have an existing Z-Finder, you'll need the new Gorilla Plate V2 for $129 US Dollars . If you're looking for the complete kit including the Z-Finder Pro, this bundle will run you $395.
Both items can be found via B&H (click here).
Zacuto Z-Finder Pro Gorilla BasePlate V2 GH3 Frame