Originally Posted by Triaged
You could also get a female inverted flare to AN-3 adapter, a pipe thread to AN-3 adapter (and remove the adapter on the slave already), and a prefabbed AN-3 flex line. Should be available at any speed shop.
...or just go to a GOOD parts store and see what they have. Front drum brake flex line sounds like a good start to me. Something like this from a '68 Impala maybe?...but it doesn't list the fitting sizes.
I tried a couple parts stores, third time lucky I actually got someone who would look something up.
Anyway for future reference BH36744 is what I ended up getting