Thxs for the replies. Now that Yakima has come out w the 15 Landing Pads, i can use my round bars. Might consider a kit to mount a 40" led bar to that, but a temporary wiring harness still elludes me. Such a bar would draw too much to use a ciggie lighter plugin solution most likely. Idea is to mount the bar for those backroad weekend excusions. Most likely would have to remove if parked at a trailhead for a weekend etc..
The current draw on LED bars is surprisingly low. My 20" draws 10 amps. I'm guessing a 40" bar would be around twice that. I rewired all my aux power plugs for continuous power with 20 amp fuses but I probably wouldn't want to run that much current for an extended time.