I've never purchased anything from Chev's of the 40's.
The caps you're talking about have to be the most readily reproduced caps I've seen for Chevy's. JC has them too:
All Jim Carter's 34-36 Caps, click here And they're easy to find made to fit custom wheels or stock wheels. Even Wheel Vintiques sells them to fit their wheels.
The caps I have are the 36-46 GMC caps from JC, but I had to get The Wheelsmith to modify them to fit my custom wheels. They're great quality caps.