This is tVNS, which means it's just a device you hold against your neck - the VNS device in the study is implanted in the neck. There's a lot more scientific evidence for the implanted device than the handheld.

For those of us who want to try VNS but not get surgery, the most proven device seems to be the Nurosym, which is an electrode that clips on to your left tragus. It's also not approved for use in the US.