I bought a pair of these cables to extend the power cables for my lighthouses since they were too far away from any power outlets. (At first I used battery packs, but those proved to be flaky).

https://www.amazon.com/gp/product/B018RW057K

What I would REALLY like is something like the JacobsParts Manual Inline DC Power Switch for the Lighthouses, rather than for the HMD power line, that way I can go and flip the switches rather than unplugging them every time I'm done. I use those remote power switches for other things in the house and I'd rather not have overlapping signals.