There is a threaded piece that will fit onto the flare nut, but the inner thread diameter is too small to fit into the coupling, so you'd have to glue it into place. The problem with this piece is that it has a nub of some sorts in the middle that has to be cut off (basically cutting the piece in half). I think I have seen this piece without the nub before (of course this was after I had finished my gauntlets), so I will check around and see if I can find it again.
::Edit:: Oh, FYI, the coupling will be found with the air tool fittings and the flare nut will be found in the plumbing section.