The remotec controller is available in the US is well. There’s already a community created device handler for it. Note that it is much smaller than it seems in most product pictures. Here’s Eric’s picture of it next to a minimote.
Also, as far as repeaters go, back in early generations of zwave we needed single-purpose devices for that, but now days pretty much any mains-powered Device except smoke sensors will work as a repeater.
Zigbee repeats only for zigbee, Z wave repeats only for zwave, so do check the protocol to make sure the repeating device is the same protocol as the one you’re trying to get signal to.
So it’s typically better to get a Z wave plus pocket socket or plug-in sensor rather then the old single purpose repeaters. You’ll get much better range with Z wave plus and you might as well get a second use out of the device.
The SmartThings branded pocket socket is zigbee so it won’t help with the popp wall controller, but there are lots of Z wave ones available.