I need master cylinder fitting

Ok so I'm working on plumbing the Wilwood disc brakes on my 68 Barracuda. What I'm looking for is the 3/16" brake line nut that fits the rear reservoir on a aluminum MP master cylinder so I can make up the line that goes from the rear reservoir to my Hurst Line loc. I've searched on line but can't find out the size I need or where to get one. Thanks