At NAB 2023, Vaxis was showing a new wireless TX cradle with pass-through power that was designed in conjunction with Core SWX for the ARRI Alexa 35.
Essentially it is a dual voltage pass-through cradle with either V-mount or AB Gold mount plates on either side. You can attach it directly to the ARRI ALEXA 35 (if you have an AB Gold mount or V-mount plate) and then your wireless TX sits in the cradle that goes between the camera and the battery that sits on the back of the plate.
Now, the cradle isn’t going to directly supply power to your TX, but it does have two D-tap ports on it that you could use, or you could power it directly via the camera.
The cradle has a nice quick-release plate that slides inside that you can attach select TX units from Vaxis and Teradek. This feature keeps the TX unit in place so it won’t move around.
These should be available in the next few weeks for around $500 USD.