Practically all grinders retain
some grounds, so it may be easier to decide if you accept that there will be 3-4 grams of waste when switching coffees. Or you may want to get a second less expensive grinder (e.g., Le'Lit PL53). If you're willing to sweep the chute of a Mazzer, the loss when switching grounds is less than 2 grams. Unfortunately your Mazzer Mini Electronic's static reduction and accurate metering depends on the exit chute screen, otherwise I would advise you to simply remove it and buy a package of small brushes.
Acid brushes from the paint storeAnother option to keep your eye on is the
Baratza Vario; it promises programmable grind settings and little waste. It reportedly is due out in August...