- Leviton still makes their VCRZ4 and @mwav3 has updated the DTH for the new app. It fits your requirements: mains powered, single gang, multi button, Z wave. But it’s very expensive, typically around $150. It’s still available for through installer channels, it’s harder to find retail but you should be able to find one. Again, just expensive.
(Note that this is not the VRCS4. That one relies on local scene controls and will not work for your purposes.)
Leviton also has a brand new Wi-Fi version of this device which cost about half as much. It does work with IFTTT, but I don’t know if it works directly with smartthings yet.
https://www.amazon.com/Leviton-DW4BC-1BW-Controller-Required-included/dp/B089VKHX8R/
- Eaton Cooper makes a similar device, again, mains powered, Z wave, single gang.
This one has a very complex set up. @nathancu has done some work on a DTH for it, so look towards the end of the following thread, the original version won’t work with the new V3 app.
[OBSOLETE] Cooper Aspire Scene Controller RFWC5 and RFWC5D Device Handler [beta release]
Comes in two different styles, one with a curve and one with a straight edge. Typically cost around $115, but you’ll have to shop around.
https://www.amazon.com/Eaton-RFWC5AW-ASPIRE-5-Scene-120-volt/dp/B0053ZIRWK
Gordon should have it in stock in both styles and several colors, but is usually one of the more expensive sellers.
https://www.gordonelectricsupply.com/p/Cooper-Rfwc5Sg-5-Btn-W-M-Scene-Cntrll/6046856?gclid=EAIaIQobChMImuvgrIeO7gIVIxmtBh3dAQq7EAQYASABEgKB7_D_BwE
.
https://www.gordonelectricsupply.com/p/Cooper-Rfwc5Aw-5-Btn-W-M-Scene-Cntrll/6046854?gclid=EAIaIQobChMImuvgrIeO7gIVIxmtBh3dAQq7EAQYBCABEgJvkvD_BwE
( The suffix is the color code, like SG for silver granite, AW for alpine white, etc.)
I think that’s it as far as what is currently available, unless somebody else knows another one.