As my title says. Who makes them, or can they be done via spare parts. It seems that if they stop manufacturing light sabers to their enemies, they would then have balanced the force.
There are no Lightsaber manufacturer company which makes profit by selling Lightsabers. Lightsabers are almost always constructed by the wielder to match his or her specific needs, preferences and style.
In fact, Lightsaber construction is mandatory skill of a trained force user which can be seen in this dialogue (from Star Wars Episode VI: Return of the Jedi):
There are some rare cases, however, in which a wielder uses a Lightsaber constructed by others: