They are hard to come by these days, but you can make one by taking a nickel plated tube and polishing off the plating.....leaving the beautiful brass. I'm leaving the threads alone since they will be hidden and the plating will eventually wear off on it's on.
I love me some brass on my GGTS's.
You can do the same on the nickel plated battery end cap.

I love me some brass on my GGTS's.

You can do the same on the nickel plated battery end cap.