That is an female inverted flare fitting used for gas and brake lines. I just went thru the same issue not finding them at any local parts store and I visited them all. I ended up ordering it from MSC. They had exactly what I needed, it was cheaper that any of the normal venders. I ordered 4 fittings and the total order including shipping was just over 18 dollars. The best part was it came in two days!
[LINK]I didn't think of MSC, had I seen your post a few min prior, I might have gone that route.
Summit always has my stuff here in 2 days, so I will stay focused on that perk.
