Another idea . . .
Look at the last few pages of The Outdoor Message (assuming that you are a GOAL member). They publish the match schedules as provided by the sponsoring clubs (if they are GOAL-affiliated clubs), so there is a reasonably comprehensive list there.
Also, I "assume" that NRA might publish a complete list of sanctioned matches somewhere on their website. Might take some digging there. [I'm not a competitive shooter, so I've never looked there.]