If you are looking for a solution with around 1 PPM free chlorine dioxide, use 1 drop of Miracle-Mineral-Supplement in 1 liter of water.
Actually, 1 drop of Miracle-Mineral-Supplement is about 0.056 ml, and in 1 liter of water that will give you about 7.5 PPM available chlorine dioxide and about 1.5 PPM as free chlorine dioxide. This is a little more than the 1 PPM you are going for, but it should be close enough.