24V AC to 12V DC Convertor, 1.5 Amp Supply Current Power Adapter with 2.1 x 5.5mm DC Power Male Plug Pigtail for CCTV Surveillance Security Camera, LED Strips

Great guide! I was able to hook up two doorbells pretty easy to the doorbell light. What box do you use to put the Shelly in? The only issue Iv had is the face plate connectors are too deep to fit into the box with the converter link images