Technical Chevy/Dodge master cylinder cap

I have been searching everywhere for a source for master cylinder caps that fit Chevy cars through 54 and Dodge trucks through 55. The thread appears to be 3/4-18. You can buy a new master cylinder with a new cap but can't find just the cap alone. Someone must make them for all the new master cylinders. any help locating a source would be helpful.

 

Too bad you don't have a friend with a lathe.

 

I do have a friend with a lathe but since they are already being manufactured why reinvent the wheel. I am making remote fill reservoir kits that look vintage for old cars, I have the 1-5/8" and 1-1/4" caps figured out and sourced. The 3/4-18 one has been elusive.

 

Still looking for a source, but have an old one in my hand to take to the machine shop

 

I have them machined at my local machine shop now and have them for sale below in my signature file.