I'll add another voice in favor of the Ecolink. The Monoprice Stich ones you looked at won't work because they're proprietary (and I think Wi-Fi?), but Monoprice does make similar Z-Wave sensors, including one that looks a lot like the Ecolink. That one won't work easily, though, since it requires the "internal" sensor to be closed before the external ones will read. You can achieve this by gluing the magnet to the side of the sensor or soldering between the contacts (that's what I ended up doing).
Like the above, I'm not aware of any Zigbee sensor with external contacts. If you're still opposed to Z-Wave (a repair is recommended if you move devices, but it still has some self-healing capabilities), you could also use something like HubDuino, but that might be more work than you're willing to set up for just this one project (but that would get you Wi-Fi for this sensor). If you're not opposed to soldering, you could also attach your device to the internal contacts of any reed-switch contact sensor. I'm guessing the Iris v2 contact sensor (model 3320-L/3320-L2) would be one, but I think some newer sensors might have moved to Hall Effect sensors instead of reed switches, which would make this more difficult to pull off.
But I'm also not sure why you'd want to move the sensor. You can make Hubitat give you alerts, so if you're still relying on the "original" device to do that, perhaps you could find a workaround using Hubitat instead (sounds like you already want something there). Most of what you what should be possible, but there is no official Alexa TTS capability. There are a couple of community solutions that may work for you there. With Pushover, you can even get differently-prioritized notifications, but with the stock Hubitat app (or most other solutions), you'll just get one kind of notification from the app.
