i use a small textured plane in front of a sector light, that works quite ok so far for some cases.
i saved that setup for me in assets lib to easy use it all time and only change gobo texture.
it not works goof for absolute sharp gobos though, and i think is slower than a pure textured light might be.
(i hope too of course that we get textured lights for easy gobo use like in 3dsmax corona)