Thanks, Wally, I do appreciate you taking time to look. As little current as they draw, I could stick in a very little extra 12V battery and wire it for 28V. The alternator can charge it as long as I don't wire it incorrectly.
Here is a place to try that might be able to help.
Air Salvage of Dallas. I have been there and looked around when visiting relatives in DAL. The little pieces are pretty cheap like switches, hoses, and other easily removable parts. They have a bunch of stuff removed and priced on shelves. They also have some big pieces.
Well, guys, I found a nice TC. I was looking for 14VDC, 3.125" dia. I found a 2.25", 28VDC - looks as tho it has never been used.
So, I made an aluminum plate for it so that it would fit the opening, hooked it up to 14 VDC, and . . . .. IT WORKS FINE!
It is also set up for 4 min turns, instead of two min, so when I make my usual 45 deg. bank turns, it really leans over. But, instead of the old Cessna-style pendulum, it has an honest ball in a glass tube, and is much more honest than the old pendulum was.
Thought it might have been that R.C. Allen one you found, Wally, but it was made by someone else, and says something about "Prop. U.S. Gov't." Has a USAF P/N on it.
Appreciate all who took the time to look and/or comment.