I'm in the process of completing my diff install and found that finding fittings for the 5mm air line is a pain. I've come across a source for 5mm push-to-fit fittings and figured I'd share.
If you want to run an airline right out of the ARB compressor without the solenoid you'll need these.
5mm Tube x 1/8" Male BSPT 90[DEG] Nickel Plated Brass Push-to-Connect Swivel Elbow
If you want to make a 90 degree turn and don't have the space required for the large bend in the plastic air line you'll want one of these.
5mm x 5mm Tube 90[DEG] Nickel Plated Brass Push-to-Connect Union Elbow
And if you need to make a quick repair to a cut air line you'll definitely want some of these.
5mm Push-to-Connect union
If you come across other fittings please post them.