It isn't a kit, but I bought one of these from Etsy six months ago and it's been working perfectly. It's mounted on the house of a friend who lives at the top of the highest ridge in my area. I went from seeing my three nodes to seeing close to a hundred.
Also, for people asking about use cases, Meshtastic doesn't do anything you can't do better with a phone. Aside from fun, it's great for at least two scenarios. If your local cell towers stop working (natural disasters, power outages, etc.) the mesh provides emergency communication. If you're going to a protest or other event where you would prefer not to be tracked or monitored, Meshtastic is far less likely to attract official attention than a phone.