AWB Enterprises can, and does, make 12x20 (and other holdes).
Alan is very responsive and will give you an honest estimate of the length of time it takes. His work is excellent. I've had 6 of each 7x17 and 12x20 holders since 1995 and have had NO problems with them. He can also custom build hard cases for your holders - I use these for transport.
Gary -- maybe its time to cancel and find another source?
I have not ties with AWB, other than a satisfied user.