Unless you are partial to the glass blocks, consider replacing the whole window with a vinyl replacement window. You can get frosted glass for privacy.
It appears that you have a vent at the top of the blocks. An operating window would solve that problem.
If you are trying to make the window smaller, then you might add some framing at the bottom, but don't forget you have a brick window sill on the exterior which you may want to remove.
All in all, a replacement window make a lot of sense.
BTW; I'm not in the window business