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And a +1 for TraCoun's courses!

The trick is that instructor courses must be taught by an NRA Training Counselor, and those are far fewer between than certified instructors.

I'd recommend searching regularly for instructor courses that interest you at http://www.nrainstructors.org/searchcourse.aspx. Most listings include email addresses, and if/when you find courses that are at least nominally close to Austin (e.g., San Antonio, Gatesville), I'd drop the Training Counselor an email and ask about any future classes near Austin.

If you can help arrange a venue and promote the class, a Counselor may well be willing to travel to you and teach the courses in Austin.

BTW, the NRA Basic Instructor Training (commonly referred to as "BIT") is a prerequisite for any firearms trainer certification like Basic Pistol Instructor or Basic Rifle Instructor. That's a one-day course needing seven classroom hours, so you might decide you could drive to San Antonio for that one. The Pistol instructor class requires a minimum of 10 hours, so is almost always spread out over two days.