Finally, success to report! I was able to secure a second ignition key from the parts department at Lou Bachrodt Chevrolet. I think I was only successful because they sell and service the large Chevy and Isuzu trucks. The key also seems to self-program by starting the ignition with the original key, wait for all the warning lights to go off, then turn off the ignition. Insert the new key within 10 seconds and start up the vehicle. It worked! Surprisingly, it was $49 for the blank and getting it cut at the Chevy dealer; I had expected to pay over $100. The RV dealer is supposed to reimburse me.
For those who have asked, I've attached a copy of this elusive item. The parts guy at the Chevy dealer told me not to lose the original. He said a replacement would be over $500 and the unit would have to be towed to the dealership.