Using a "travel router" connecting to a NAT'd target without static IP.

So... the client end, I THINK is fairly easy. There's tonnes of travel routers. I assume I need to find one that can have one of it's interfaces set up to talk wireguard.

What's the smallest/easiest way to setup a (preferably wireguard) box, behind my router at home that can reach out and update something with the new dynamic IP to use for a travel router to target?
I'd guess it's just port forwarding to router?

A small box that "just work" would be ideal.
A "follow this guide" idea for something windows/linux based (maybe something that'd work on a raspberry PI/similar?) would be a good 2nd.

https://redd.it/1wdc9tt
@r_wireguard