The air hose connector on the left in your first photo is a NAPA style D connector. They are very common in South Eastern US. If there is a NAPA store near you, you can get the style D connectors there.
eae197, way back when I built it, I thought 30 x 40 was large. I can't turn around in it! I am envious of the folks here who talk about their 30 x 70 or 40 x 100!
amalik, NAPA stores are not really franchised, but many are independently owned. About 1/3 of them are Company owned and the rest are owned by individuals.
I just retired from owning a NAPA Auto Parts store for 36 years in East Tennessee. Just trying to catch up on projects I have been putting off for over 30 years! I am a man of many interests and have just enough knowledge to be dangerous in all of them! I like quick cars, carpentry...