You could show us a photo of your meter. Chances are good, that there’s also a magnet, if there is the reflective bit.
If you only have the reflective bit: I doubt there’s a readily usable sensor for that. In that case, I’d try to hack the output of a reflective light barrier sensor to a zigbee window sensor. From there on, there are known solutions.
If there’s a magnet: Skip the hacking bit and just use a window sensor. Like this: Gas meter from Xiaomi/Aqara door sensor (ZigBee)