light bars?

Check out the bigger junk yards Easy, up here they leave them on the vehicles if their older. Check out the old highway trucks, either state or county, should be able to get one for $50. or less. If you end up with red/blue light bar you can buy new yellow lens for them. You can buy a small revolving one for about $39. new but the bulb inside is kind of whimpy, not a real bright light.
Also if you have a large truckstop around you check their store, alot of them carry smaller revolving lights for the guys hauling oversize loads.