Well the project is that my girlfriend’s bike should have a bit taller handles. So I took it off (good old trick to remove the grips: inject some soapy water under them) and went to a shop to buy a taller one.
They had none and told me to go to another shop. In the other shop they said they had none and it’s pretty dangerous to just make the hande post longer because it can break and you can die. (But at least break a few bones.)
But the guy said maybe it’s possible to make the handles themselves longer. I will see what I can do.