Mains powered door sensor/contact sensor?

Hardware
1

I have a couple of home automations that I’d like door sensors for, I absolutely despise batteries, so I’d like something I could run from the mains.

Ideally WiFi, but would be okay with Zigbee or Zwave.

A solution I was thinking of would be to use a typical off-the-shelf reed switch (i.e for a typical alarm system) and and wire it up to a shelly or similar. The problem is the shelly is either high voltage AC (which I cannot use directly with these low voltage reed switches) or low voltage DC, not both. It would be nice to avoid a power supply.

Does anyone know of any hardware I could use to achieve this?

2

The Shelly i3 contact voltage is actually very low, I did measure it at some point and I think it was under 5V.

3

@simtr Did you find a solution? I wish to do the same thing.
Thanks

4

This may work: Battery Eliminator - CR123A, 2 Cell Battery Replacement, - AC Source, 6VDC