Lights that turn on when others are ON
You'll need to get power to it somehow.  What I'm thinking is surface conduit from your existing switch or light to wherever you need to go.  Simply run the switched-hot through the surface conduit to where you need to be. 

Surface conduit such as Wiremold is fully code legal and allowed for permanent wiring, which saves  you doing some goofy, illegal horked up thing. 

Or if the problem is getting switched-hot to the switches, but you can run always-hot to them, then go with X-10 or some other smart-switch control system, of which there are plenty today.  (X-10 goes back to the 1970s).  

You could also consider low-voltage lighting if you don't want to use surface conduit, the rules for cabling low-voltage circuits are relaxed as compared to mains circuits.