In the photos, your stem has already been removed. I think what you are calling a stem is actually the steerer tube. You will not be able to replace the steering tube without replacing the entire fork (that's an option, btw).


Also, you might be able to avoid the whole steering tube extender thing by buying a handlebar that has more rise. This, in addition to a more angled stem, can raise the front end by several inches if you want that.



If you want a Jones-style bar like in your photo, Jones makes one with 2.5" of rise: