All stylus I've seen weigh a little because what it is and must do. All have less than reliable responses. You should forget this and consult with those that work in this field for other solutions.
I have tried to use other styluses before but the effort required was too much. The stylus i need would not be used in the hand, so when i say "no effort" i do not mean, little. I am looking for a stylus that is very lightweight (again this is for a special needs client) and that is virtually effortless for the screen to respond. Two tries and two failures in attempting to find suitable products. First one had a "very low effort" rubber looking tip. Was too heavy and required too much effort to get reliable response. Second weighed even more. This application will be on the end of a mouth stick, held in by your teeth, 6 inches out. Literally no effort needs to be required for ease of use and reliable response. I saw something on youtube from CNET at a show but could not find any solutions in any search. Any help is appreciated