The enclosure is from a floor heating package from the company Ebeco. I got this over when we remodeled our bathroom. Ebeco seems to be a Swedish company, but i think there should be other good enclosures available since the LCD screen size (1,8" / 36x28.7mm) is quite common. Here is a link to a swedish store.
This fits inside a standard Schneider wall frame. The frame and Ebeco enclosure was glued to a metal frame which can be attached to the in wall box with screws.
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For this project i use my 240 to 5v node. It holds both power, MCU and nrf24 radio. LCD, buttons and LED are connected to the MYSX gpio on this node. Please read more here: https://www.openhardware.io/view/13/In-Wall-ACDC-Pcb-for-MySensors
If you have 5v in another way you can do this by wiring an Arduino Pro mini and Nrf24 radio as usual.
As always - if you decides to use this know it is high voltage power = do it on your own risk - I cant guarantee your safety.