It was never expressly forbidden, but I've never known anyone to actually make one. Apparently they were used during my grandfather's time.
Power cells I have to build myself, because I really doubt any handheld Earther technology could support a lightsaber. I have a few to spare if you need one. My brother got his focusing crystal in the core of a gas giant, but you probably can't do that. Mine's a lambent, a living crystal, and my sister actually made hers artificially. You might want to do that, if you know how. My sister's kind of a genius.