Meshtastic

I'm not aware of any ready-to-use ones you can buy that are outdoor rated. Pretty much all of the pre-assembled ones I've seen are in a handheld or portable form factor.

For a "repeater" node (note the quotes, explained further below), I've wanted to pick up one of the new 1 W high power Rak Wireless boards (link). Those have a battery terminal as well as a solar input for charging. All you'd need to add would be a PV panel + battery and put it into some kind of housing. I'd also use a nicer antenna than the little stub one that comes with it.

You should be able to put that together without any kind of soldering, though you would need to wire the solar panel output to a battery-style connector to be able to attach it to the board. There are solder-free wire splicers you may be able to use, but it's also a good opportunity to practice soldering as there's little to mess up.

For the housing, you might look for outdoor-rated utility boxes or something like that. Would probably have to drill and seal holes for the antenna connector and solar panel wire, but shouldn't be too difficult. That, or you may be able to get a friend to help with 3D printing a solution.

Now, back to the use of "repeater" instead of repeater. Meshtastic docs are very adamant about only using the repeater role (now "router" role; repeater has been deprecated in recent versions). In all but the rarest and most optimally placed cases, you'd want to be using "client" or "client base" modes as they repeat messages but without forcing other clients to use them (and thus consuming a hop).