Hey, I know this is a niche model but as I needed it I hope somebody else may benefit from it in the future. I modeled this after the ATH-A900X Left earcup holder pretty accurately and I'm really happy with the results, it looks spot on. I'm pretty sure it'll fit other similar headphones with the same driver size from Audio Technica like the A700Xs but you'll have to test that. The part is modeled after the left speaker holder but I'm pretty sure mirroring it will work for the right speaker holder. The model is pretty much the same as the original part so all the parts that fit onto it should fit no problem (circlip, a brass bushing that the cable goes through to remove friction, and two pins that limit the axis). I made a few tweaks to the model which I haven't tested myself based on my final assembly, I don't think there should be any issues but if there is something you need me to tweak for it to work better let me know. I suggest printing in the same orientation it comes in when loading it into the slicer, as the upper part is the outer part of the headphones and that's the part that you will see once assembled. This part was inspired by the part made by @PeterTo on Printables and based on the original Audio Technica part.
The thing with replacing this part is that you need to desolder the cable that goes between the left and right earcup but I've done this twice, basically a two core wire it's not that hard. Hope someone else gets to enjoy this model and good luck!