Do you have tri-clamp fittings?
I think that is the best way to make a rotating arm.
Here is what I would do, and I would source the TC parts and the ball valve from KLG Stainless on Ebay. He has the best prices and Kevin is very nice to deal with.
Bargainfittings.com is great for the locknut, washer, half coupling, and o-rings.
You will need to find someone to weld the dip tube in for you.