Actually, the Zooz ZSE18 is a repeater if you pair it when it's powered via USB (and keep it that way, since it will eat batteries way too fast if switched then). See: Add Your ZSE18 Motion Sensor as Signal Repeater on USB Power - Zooz Support Center. The ZSE29 can also be powered via USB, but what I've heard about it makes me think it wouldn't be a repeater regardless.
USB makes it easy to use things like battery packs or alternative power methods when mains power is lost without the need for a "real" UPS. A motion sensor won't care if it loses power for a second or two during the transition, unlike, say, your hub. You could even use something like this, again without caring whether you get a specific model that does or doesn't lose power during the transition: DIY- Battery Backup Hubitat- under TEN bucks-NO soldering (I have one for my hub after finding a model that works well for that...and several that don't that I've contemplated using for USB-powered repeaters). But here, even one of those "travel USB battery pack" things would work.
All of this just might not look pretty depending on where the sensor is located. 
But as mentioned above, you may still have problems, depending on what specific devices your devices are repeating through.
I've also heard good things about the Ring Extender (Gen 2) and it's on my "to buy at some point" list, but from what I've read they'll only work well on a C-7 (with S2 like the want). With some work, they can a pair to a C-5 or older and likely repeat fine, but people have had problems getting attributes reliably reported in the UI (which for those are particularly nice since they report AC vs. battery power that you might be able to use for other purposes, like telling when you have a power outage).
