The Olympus VF-1 is an optical viewfinder with a view corresponding to a 17mm lens. The Panasonic VF1 has bright lines corresponding to 24mm. Neither is a good fit for the 50mm lens. I would try to get an electronic viewfinder for your camera - they will work with any lens.
If the VF1 has a 24mm frame that would be about double of the 50mm. However it would be framing a much larger area and thus hard to use. Get a VF2 or 3 EVF!!! They work great for adapted lenses and since you can use the magnify view for focusing it makes getting sharp images a snap.