Dix Bruce and David Grisman dedicated Vol. VI, Issue 1 of their publication Mandolin World News to the electric mandolin. There's a lot of good information on the instruments that were available at the time (1981). You can order copies from Dix at his Musix Web site.
Joel Glassman penned an article for MandoZine that describes his efforts to build his own electric mandolin, and lists some players and recordings. Joel has been of invaluable assistance in helping me track down other players and builders.
Thanks to Julio Moreno for the information on Brazilian players.
I also greatly appreciate Will Meister's scouting help. It's nice to know that people besides myself are interested in this stuff.