Once you open the shifter up.. all you need to do is stuff a slot where spring is so that it gives more resistance..
I did it.. and its more resistance from vanilla shifter, its still not as resistant as his in the video.
There was a site with some pictures, but seems its down.
Just take it apart your self, its not that hard... Ull find a ball and spring inside white plastic casing, just make sure you secure where the spring about half way and insert the spring back.