ATWOOD Hydraulic brake actuator parts

Hi and Welcome to the T@B Forum

I have no direct experience however web searches note . . .

With Atwood out of business there aren't any exact replacements for hydraulic couplers generally available. Most web-articles suggest:
1] searching local boat trailer shops to see if they have old (dusty) stock.
2] doing minor modifications to other brand/model parts to fit your Atwood.
3] replacing full Actuator with an available today brand,
      replacement cost should be <$200 or so + installation
      DIY installation is possible (option I would select)

Here's an Atwood exploded diagram, from

https://www.pacifictrailers.com/blogs/boat-trailer-tips-advice/atwood-hydraulic-brake-actuator-parts-list-and-schematic 

There is a good reference article here:

https://www.etrailer.com/question-374377.html

Let us know your final solution.