That seems like a good start. What about your state's (or maybe even your city's) Arts Counsel? A lot of times they have grants available or hold contests for screenplays, fiction, etc. A private backer might be extraordinarily hard to come by in this economy. If it were me, I think I'd find the way off broadway set and show the screenplay to a few actors. That or try to put your own troop together and rent an auditorium.