Here is a Delrin shift knob that also works as a shift shortener.
Because the thread is inserted much deeper internally then a normal shift knob, it lowers the total height of the shift rod assembly and as such shortens the lever throw.
Delrin never gets hot and never cold and is virtually shatterproof.
It is often used to replace rubber suspension bushings on "performance" vehicles and needs no lubrication.
It really looks like a "joy stick" and truly is.