I replaced the brake master cylinder on my 1954 Chev 3100, and also couldn't find a replacement Banjo bolt fitting, so I bought new copper compression ring and reused the old one.
I would like to find a new one if possible.
Below is a picture of it.

Attachments
20190117_184929.jpg (213.01 KB, 94 downloads)
Banjo Bolt

1954 Chev 3100 Truck - Mostly all "Original"
https://lh3.googleusercontent.com/4...7X26uneH2rb3222fNY4s7FvnKH=w1697-h954-no