Good news folks. Today I was checking with a neighbor (he worked at the local NTB) asking if NTB would mount tires I didn't buy there. He told me they will for $20 each, mounted and balanced.
I called the store to also check if they would install my TPMS monitors for me. On a whim I asked what tires in ST235/80-16 load range G were offered. I had checked their website and it only showed two choices in load range E.
The salesman said yes they had several, Sailun was a choice. They were the S367. Price is $142 each, $3 more than current Simpletire price. They did not stock them but would only take 1-2 days to have them in hand.
My point to all this is that they are available at a National chain. If one is traveling and has a tire issue it seems reasonable we should be able to find an NTB that works in our plans and get a replacement if needed.