Mcmaster has them in 1/8, 1/4, 3/8, and 1/2. But no 3/16". Durn! BTW, they call them supported 45 degree brass flared tube fittings. Never heard them called that before. They were inverted flares ever since I was a pup.
The part number for the complete pipe & nuts assembly is 277213, listed as not available. Try some of our guys that have NOS parts in stock.