The 40" and the 10" together will draw more current than the typical 20 amp switch will handle. So you will need a relay for each light bar for what I propose. Use the single switch to energize the relays. A single DPDT center off switch can be used for both lights.The switch will allow you to either turn the 40" on or both at the same time with center being off. Feed +12VDC to both center poles of the switch. Use one side for the 40" relay coil and the other side for the 10" relay coil. On the 40" side jumper both outer poles together and then a wire to the relay coil. The 10" side you just use one pole to the coil. The power for the actual lights will be from what ever you choose for primary power thru fusing or breakers for each light.