I am an NRA Instructor in Handguns, Rifle, Shotgun, Personal Protection, and Home Defense.
The guy that taught me is long dead. I took the classes over a period of nights at the public library. We went to the range for the hands-on parts.
It was difficult to find a qualified Instructor Trainer. As you've found out, there is a shortage.
My only suggestion is for you to continue to "bug" them to give you a list of names of Trainers.
I have found that being "Certified" came in handy when I taught Boy Scouts, Royal Rangers (a church group), etc. Many organizations require "Certified" trainers for their programs.
Good luck to you.
Edited to add: Dolomite, in his usual charming way (
), is correct.
I've also attended Thunder Ranch and the quality of the instruction is a thousand times better than the NRA training. The NRA stuff is very basic. You will not learn much new.
But it does give you the "Certification" I spoke about.