Friend of a friend, an old tire guy who runs his own auto tire & repair shop, patched the tire for ten bucks.
He used a liner patch -- roughed up the inner tire liner just enough to eliminate the texture (not too deep), cleaned the liner area with solvent to remove all the silicone mold release, applied cement and let it dry, stuck the liner patch and stitched it using a roller to firmly press it down. He also said he used fire somehow at some point to remove oxygen, though I wasn't clear exactly how or whether this was truly necessary.
He said he's patched many tires this way, and as long as it holds air once mounted it should be good for the life of the tire.
I've also seen recommended, as a good idea for steel belted tires, to fill the hole with a rubber stem to keep water from getting into the belts, though typically little damage has been found from unfilled holes in failed tires. I'm thinking maybe put a little glob of tire cement in the hole and let it dry just to add that measure of safety.
Still a good idea to keep an eye on the tire after that, but us riders do that anyway.
Since I've already got a new tire mounted and installed, I'll keep this one as a backup or for the next tire replacement. It'll be nice to get more than 300 miles out of this otherwise brand new Road 6!
Cheers! Dave