hi karel, here is another suggesion, next time you are in the supermarket find the deodorants, look for right guard, take off the plastic cap, turn upsidedown and imagine a paperweight displayed on it. i have tried it and it works! the higher the dome of the weight the better it works, just as the shallower the dome the less it works. there may be tops that work better, but i just had some right guard to hand.
kindest regards theglassnut...