If you are referring to the M6 elbows, here is a response I copied from an earlier forum update where I shared this and other work:
I didn’t use any special hose for a main line, just 4 mm OD tube and a manual pump oiler. Both from Amazon I believe. The oiler has two output ports, so I just made the lengths equal to try and keep the oiling consistent. I believe at the time the wait for M6 x 4 mm OD elbow fittings was too long, so I sourced them from Mettle Air, but I think they are on Amazon now and readily available.
Here is the forum update link - there is a lot there, but it has a few photos of the oiler, lines, and fittings: