Well this is not a software project using Home Assistant but rather HW to enable automation in Home Assistant.
I hope it can fit anyway 
So, I have the old Swedish AGA valves on my radiators and wanted to fit eQ3-MAX! now that they are supported in Home Assistant. I needed two adapters per radiator which wasn’t good looking and not cheap either.
And so I designed my own for 3D printing.
If you happen to be in the same position as I, feel free to download the adapter from thingiverse and save yourself some trouble and money