I’m not sure why, it may be a safety regulation with regard to DIY work, but there literally are not any devices of this form factor on the certified zwave list for the EU region. Just plug-in pocket sockets and in wall relays.
http://products.z-wavealliance.org/regions
There are definitely lightwave RF versions which you could consider (although I don’t think any have a USB socket). Adam Clark has done a SmartThings/lightwave RF integration, but it does require some significant technical skills to get it set up. And you do have to set up your own server on raspberry pi. So it’s not simple, but it can be done
Rather than just looking at the code in GitHub for an integration, I always recommend that you start with the author’s thread in the SmartThings forum. That way you can see some of the discussion about it and ask any questions you might have.